125876 + Interview Questions in General QA

1.	Who are the main contributors of modem : synthetic theory of evolution?
Answer» R. Fischer, J. B. S. Haldane, T. Dobzhansky, Huxley, E. Mayr, Simpson, Stebbins, Fisher, Sewall Wright, Medel, T. H. Morgan, etc. are the main contributors of modern theory of evolution.

Discussion

2.	Describe in brief the palaeontological evidences of human evolution.
Answer» i. Man originated from ancient apes. ii. Fossil bones of human ancestors were discovered from Africa, Germany, China, France, Java and other parts of Asia. iii. The available fossils are skulls, teeth, mandibles, bones like humerus, femur and stone implements. iv. These fossils belong to different geological ages. v. The four main stages in the origin of man are – Ape stage, Ape-men stage, Primitive men (Prehistoric man) and Modern man. a. Ape stage: Primitive apes was the ancestor of man which lived 30 million years ago. Propliopithecus was the primitive ancestral ape. This gave rise to Dryopithecus. b. Ape-man stage: This stage is intermediate between apes and man. The important ape-men include Ramapithecus, Kenyapithecus and Australopithecus. Australopithecus was the connecting link between apes and primitive man. c. Primitive man (Prehistoric man): It was the first true man. Following are the important primitive men: 1. Homo habilis (Handy man) 2. Homo erectus (Java man and Peking man) 3. Homo neanderthalensis (Neanderthal man) d. Modern man: Homo sapiens fossilis was the extinct modern man. The modern man of today is called Homo sapiens sapiens.

2.

Describe in brief the palaeontological evidences of human evolution.

Answer»

i. Man originated from ancient apes.

ii. Fossil bones of human ancestors were discovered from Africa, Germany, China, France, Java and other parts of Asia.

iii. The available fossils are skulls, teeth, mandibles, bones like humerus, femur and stone implements.

iv. These fossils belong to different geological ages.

v. The four main stages in the origin of man are – Ape stage, Ape-men stage, Primitive men (Prehistoric man) and Modern man.

a. Ape stage: Primitive apes was the ancestor of man which lived 30 million years ago. Propliopithecus was the primitive ancestral ape. This gave rise to Dryopithecus.

b. Ape-man stage: This stage is intermediate between apes and man. The important ape-men include Ramapithecus, Kenyapithecus and Australopithecus. Australopithecus was the connecting link between apes and primitive man.

c. Primitive man (Prehistoric man): It was the first true man. Following are the important primitive men:

1. Homo habilis (Handy man)

2. Homo erectus (Java man and Peking man)

3. Homo neanderthalensis (Neanderthal man)

d. Modern man: Homo sapiens fossilis was the extinct modern man. The modern man of today is called Homo sapiens sapiens.

Discussion

3.	Explain modern synthetic theory of evolution.
Answer» Julian Huxley proposed term ‘modern synthesis’. This theory was based on the work of Dobzansky. The salient features are as follows. i. According to the Modern synthetic theory of evolution, population is considered as a unit of evolution because new species are evolved from a population and not from a single individual. ii. A group of similar individuals interbreeding among themselves, occupying a geographical area is called genetic population or Mendelian population. iii. The sum total of genes of all individuals of interbreeding population is called gene pool. iv. Every gene pool has different genes, each having their own specific gene frequencies. v. The Modern synthetic theory is based on three main concepts, i.e. Genetic variations, Natural selection and Isolation. a. Genetic variation: 1. It is the change in gene and gene frequencies. 2. It is the raw material for evolution. 3. Genetic variation in populations is caused by  Gene mutations, Gene flow, Genetic recombination, Genetic drift and Chromosomal aberrations. b. Natural selection: 1. It brings about evolutionary changes by favouring differential reproduction of genes that bring about changes in gene frequency from one generation to another. 2. Natural selection invariably encourages those genes that assure highest degree of adaptive efficiency between population and its environment. c. Isolation: 1. Interbreeding does not occur between two isolated groups. 2. Each group may develop a set of new traits that lead to evolutionary changes and towards formation of new species.

3.

Explain modern synthetic theory of evolution.

Answer»

Julian Huxley proposed term ‘modern synthesis’. This theory was based on the work of Dobzansky.

The salient features are as follows.

i. According to the Modern synthetic theory of evolution, population is considered as a unit of evolution because new species are evolved from a population and not from a single individual.

ii. A group of similar individuals interbreeding among themselves, occupying a geographical area is called genetic population or Mendelian population.

iii. The sum total of genes of all individuals of interbreeding population is called gene pool.

iv. Every gene pool has different genes, each having their own specific gene frequencies.

v. The Modern synthetic theory is based on three main concepts, i.e. Genetic variations, Natural selection and Isolation.

a. Genetic variation:

1. It is the change in gene and gene frequencies.

2. It is the raw material for evolution.

3. Genetic variation in populations is caused by  Gene mutations, Gene flow, Genetic recombination, Genetic drift and Chromosomal aberrations.

b. Natural selection:

1. It brings about evolutionary changes by favouring differential reproduction of genes that bring about changes in gene frequency from one generation to another.

2. Natural selection invariably encourages those genes that assure highest degree of adaptive efficiency between population and its environment.

c. Isolation:

1. Interbreeding does not occur between two isolated groups.

2. Each group may develop a set of new traits that lead to evolutionary changes and towards formation of new species.

Discussion

4.	Which statement is true for the theory of spontaneous generation? (a) Life came from outer space. (b) Life can arise from dead matter. (c) Life can arise from non-living things only (d) Life arises spontaneously by miracle
Answer» Correct answer is (c) Life can arise from non-living things only

Discussion

5.	What is abiogenesis? Explain the ‘Theory of spontaneous generation’ or ‘Theory of abiogenesis’.
Answer» Abiogenesis: It is the hypothetical process by which living organisms are believed to have developed from nonliving matter. Theory of spontaneous generation: i. It is also called the ‘Theory of autobiogenesis’ (auto = self, bios = life, genesis = formation). ii. According to this theory, life originated from non–living material spontaneously, without any interruption. iii. It was initially putforth by Greek Philosophers in 600 B.C. and was supported by Aristotle. iv. The Greek Philosophers believed that air, water, fire and earth are vital forces or the active principles which have the capacity to transform non–living matter into living organisms. v. Louis Pasteur finally disproved the theory of spontaneous generation and gave the scientific explanation that life originated only from pre-existing life or biogenesis.

5.

What is abiogenesis? Explain the ‘Theory of spontaneous generation’ or ‘Theory of abiogenesis’.

Answer»

Abiogenesis: It is the hypothetical process by which living organisms are believed to have developed from nonliving matter.

Theory of spontaneous generation:

i. It is also called the ‘Theory of autobiogenesis’ (auto = self, bios = life, genesis = formation).

ii. According to this theory, life originated from non–living material spontaneously, without any interruption.

iii. It was initially putforth by Greek Philosophers in 600 B.C. and was supported by Aristotle.

iv. The Greek Philosophers believed that air, water, fire and earth are vital forces or the active principles which have the capacity to transform non–living matter into living organisms.

v. Louis Pasteur finally disproved the theory of spontaneous generation and gave the scientific explanation that life originated only from pre-existing life or biogenesis.

Discussion

6.	Who conducted experiment to verify Oparin’s theory about creation?(a) Haldane(b) Jagdish Chandra Bose(c) Birbal Sahni(d) Miller
Answer» Correct answer is (d) Miller

Discussion

7.	Give the three key factors of the modern synthetic theory of evolution.
Answer» Genetic variation, natural selection and isolation are the key factors of modern synthetic theory of evolution.

Discussion

8.	Haldane described ‘Hot dilute soup’ in his theory. Describe how this soup led to formation of some important molecules.
Answer» (1) The primitive sea containing molecules of organic substances without free oxygen was described as ‘hot dilute soup or primitive broth’ by Haldane. He proposed the theory of chemical evolution. (2) According to this theory, the chemical evolution took place in the following steps : (a) Origin of earth and its primitive atmosphere, (b) Formation of ammonia, water and methane. These molecules dissolved in rainwater and formed the seas, (c) Then synthesis of simple organic compounds took place, followed by formation of complex organic compounds such as nucleic acids. (3) The early molecules underwent chemical reactions such as condensation, polymerization, oxidation and reduction. (4) The biologically important molecules such as monosaccharides, amino acids, purine, pyrimidine, fatty acids and glycerol were formed due to these reactions, utilizing the sources of energy on the primitive earth. (5) Since oxygen was lacking, there was no degradation. Enzymes were also absent and hence there was formation of complex molecules in the hot dilute soup. (6) This further led to the formation of precells or protobiont. These aggregates were called coacervates by Oparin or microspheres by Sidney Fox. This further gave rise to first cells on the earth.

8.

Haldane described ‘Hot dilute soup’ in his theory. Describe how this soup led to formation of some important molecules.

Answer»

(1) The primitive sea containing molecules of organic substances without free oxygen was described as ‘hot dilute soup or primitive broth’ by Haldane. He proposed the theory of chemical evolution.

(2) According to this theory, the chemical evolution took place in the following steps :

(a) Origin of earth and its primitive atmosphere,

(b) Formation of ammonia, water and methane. These molecules dissolved in rainwater and formed the seas,

(c) Then synthesis of simple organic compounds took place, followed by formation of complex organic compounds such as nucleic acids.

(3) The early molecules underwent chemical reactions such as condensation, polymerization, oxidation and reduction.

(4) The biologically important molecules such as monosaccharides, amino acids, purine, pyrimidine, fatty acids and glycerol were formed due to these reactions, utilizing the sources of energy on the primitive earth.

(5) Since oxygen was lacking, there was no degradation. Enzymes were also absent and hence there was formation of complex molecules in the hot dilute soup.

(6) This further led to the formation of precells or protobiont. These aggregates were called coacervates by Oparin or microspheres by Sidney Fox. This further gave rise to first cells on the earth.

Discussion

9.	Oparin’s theory is based on(A) artificial synthesis(B) spontaneous generation(C) will of God(D) all of these
Answer» Correct Option is (A) artificial synthesis

Discussion

10.	Explain modern Synthetic Theory of Evolution in brief.
Answer» (1) Modern synthetic theory of evolution is the result of modification of Darwinism and theory of mutations by taking into consideration studies of genetics, ecology, anatomy, geography and palaeontology. (2) Five key factors of modern synthetic theory are gene mutations, mutations in the chromosome structure and number, genetic recombinations, natural selection and reproductive isolation. All these finally contribute in the evolution of new species or process of speciation. (3) Population or Mendelian population is the small group of ‘interbreeding populations’. For every Mendelian population there is a gene pool which is constituted by total number of genotypes in it. The genotype of an organism in a population is constant, but the gene pool constantly undergoes change due to different factors such as mutations, recombination, gene flow, genetic drift, etc. (4) Every gene has two alleles. The proportion of a particular allele in the gene pool, to the total number of alleles at a given locus, is called gene frequency. Thus any change in the gene frequency in the gene pool affects population. (5) The five main factors are broadly divided into three main concepts as follows: (i) Genetic variations caused due to various aspects of mutation, recombination and migration. Such variations cause change in the gene frequency. Gene mutations or point mutation change the phenotype of the organism, leading to variation. Recombination is caused due to crossing over in which new genetic combinations are produced. Sexual reproduction due to fertilization of gametes also cause recombinations. All these lead to variations, Gene flow is movement of genes into or out of the population, either due to migrations or dispersal of gametes. Gene flow therefore change the gene frequencies of the population. Genetic drift is a random change which occurs by pure chance. It occurs in small populations but change the gene frequency. Chromosomal aberrations are structural or morphological changes in the chromosomes causing rearrangement of the sequence of genes. (ii) Natural selection is said to be the main driving force in evolution. It brings about evolutionary changes by selecting favourable gene combinations by differential reproduction of genes. This brings about changes in gene frequency from one generation to next generation. (iii) Isolation means the separation of the population of a particular species into smaller units which prevents interbreeding between them. This over a long time period leads to speciation or formation of new species.

10.

Explain modern Synthetic Theory of Evolution in brief.

Answer»

(1) Modern synthetic theory of evolution is the result of modification of Darwinism and theory of mutations by taking into consideration studies of genetics, ecology, anatomy, geography and palaeontology.

(2) Five key factors of modern synthetic theory are gene mutations, mutations in the chromosome structure and number, genetic recombinations, natural selection and reproductive isolation. All these finally contribute in the evolution of new species or process of speciation.

(3) Population or Mendelian population is the small group of ‘interbreeding populations’. For every Mendelian population there is a gene pool which is constituted by total number of genotypes in it. The genotype of an organism in a population is constant, but the gene pool constantly undergoes change due to different factors such as mutations, recombination, gene flow, genetic drift, etc.

(4) Every gene has two alleles. The proportion of a particular allele in the gene pool, to the total number of alleles at a given locus, is called gene frequency. Thus any change in the gene frequency in the gene pool affects population.

(5) The five main factors are broadly divided into three main concepts as follows:

(i) Genetic variations caused due to various aspects of mutation, recombination and migration. Such variations cause change in the gene frequency. Gene mutations or point mutation change the phenotype of the organism, leading to variation. Recombination is caused due to crossing over in which new genetic combinations are produced. Sexual reproduction due to fertilization of gametes also cause recombinations. All these lead to variations, Gene flow is movement of genes into or out of the population, either due to migrations or dispersal of gametes. Gene flow therefore change the gene frequencies of the population. Genetic drift is a random change which occurs by pure chance. It occurs in small populations but change the gene frequency. Chromosomal aberrations are structural or morphological changes in the chromosomes causing rearrangement of the sequence of genes.

(ii) Natural selection is said to be the main driving force in evolution. It brings about evolutionary changes by selecting favourable gene combinations by differential reproduction of genes. This brings about changes in gene frequency from one generation to next generation.

(iii) Isolation means the separation of the population of a particular species into smaller units which prevents interbreeding between them. This over a long time period leads to speciation or formation of new species.

Discussion

11.	Theory of special creation is based on ………………. beliefs. (a) scientific(b) religious (c) traditional (d) mythological
Answer» Correct answer is (b) religious

Discussion

12.	The human chromosome with highest and least number of gene is: A) Chromosome 21 and Y B) Chromosome 1 and X C) Chromosome 1 and Y D) Chromosome X and Y
Answer» Correct Answer is: C) Chromosome 1 and Y Chromosome 1 represents the highest number of genes as it contains about 2000-2100 genes. The human chromosome with least number of genes is Y chromosome. It is a sex chromosome, present in males and has around 50- 60 genes.

12.

The human chromosome with highest and least number of gene is: A) Chromosome 21 and Y B) Chromosome 1 and X C) Chromosome 1 and Y D) Chromosome X and Y

Answer»

Correct Answer is: C) Chromosome 1 and Y

Chromosome 1 represents the highest number of genes as it contains about 2000-2100 genes. The human chromosome with least number of genes is Y chromosome. It is a sex chromosome, present in males and has around 50- 60 genes.

Discussion

13.	Variations during mutations of meiotic recombinations are ………………. (a) random and directionless (b) random and directional (c) small and directional (d) random, small and directional
Answer» Correct answer is (a) random and directionless

Discussion

14.	Industrial melanism observed in moth, Biston bitularia shows ………………. type of natural selection. (a) stabilising (b) directional (c) disruptive (d) artificial
Answer» Correct answer is (b) directional

Discussion

15.	Why does the hnRNA need to undergo changes ? List the changes hnRNA undergoes and where in the cell such changes take place.
Answer» Has (non-functional) introns (Methyl guanosine tri-phosphate is added to 5' end) capping, tailing (Poly A tail at 3' end added), splicing (introns are removed and exons are joined). Nucleus Detailed answer: The hnRNA eukaryotes needs to undergo changes for converting it into functional RNA. The hnRNA contain both exons and introns. The exons are functional coding segments while introns are non functional and non coding sequences. This hnRNA undergo processing where in the introns are removed and exons are joined by a process called and splicing. Now this transcribed heterogenous nuclear RNA undergoes additional processing called capping and tailing. In capping methyl guanosine triose phosphate which in an unusual nucleotide is added to 5 end and in tailing 200-300 adenylate residues are added at 3' end of spliced RNA. This is completely processed hnRNA. This is now called a mRNA. such changes of processing takes place in the nucleus of the cell.

15.

Why does the hnRNA need to undergo changes ? List the changes hnRNA undergoes and where in the cell such changes take place.

Answer»

Has (non-functional) introns

(Methyl guanosine tri-phosphate is added to 5' end) capping, tailing (Poly A tail at 3' end added), splicing (introns are removed and exons are joined).

Nucleus

Detailed answer:

The hnRNA eukaryotes needs to undergo changes for converting it into functional RNA. The hnRNA contain both exons and introns. The exons are functional coding segments while introns are non functional and non coding sequences. This hnRNA undergo processing where in the introns are removed and exons are joined by a process called and splicing. Now this transcribed heterogenous nuclear RNA undergoes additional processing called capping and tailing. In capping methyl guanosine triose phosphate which in an unusual nucleotide is added to 5 end and in tailing 200-300 adenylate residues are added at 3' end of spliced RNA. This is completely processed hnRNA. This is now called a mRNA. such changes of processing takes place in the nucleus of the cell.

Discussion

16.	आयरन क्रोमाइट अयस्क से पोटैशियम डाइक्रोमेट बनाने की विधि का वर्णन कीजिए। पोटैशियम डाइक्रोमेट विलयन पर pH बढ़ाने से क्या प्रभाव पड़ेगा?
Answer» पोटैशियम डाइक्रोमेट बनाने की विधि (Method of Preparation of Potassium Dichromate) – आयरन क्रोमाइट अयस्क (FeCr₂O₄) को जब वायु की उपस्थिति में सोडियम यो पोटैशियम कार्बोनेट के साथ संगलित किया जाता है तो क्रोमेट प्राप्त होता है। 4FeCr₂O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂CrO₄ +2Fe₂O₃ + 8CO₂ ↑ सोडियम क्रोमेट के पीले विलयन को छानकर उसे सल्फ्यूरिक अम्ल द्वारा अम्लीय बना लिया जाता है। जिसमें से नारंगी सोडियम डाइक्रोमेट, Na₂Cr₂O₇ . 2H₂O को क्रिस्टलित कर लिया जाता है। 2Na₂CrO₄ + 2H⁺ → Na₂Cr₂O₇ + 2Na⁺ + H₂O सोडियम डाइक्रोमेट की विलेयता, पोटैशियम डाइक्रोमेट से अधिक होती है, इसलिए सोडियम डाइक्रोमेट के विलयन में पोटैशियम क्लोराइड डालकर पोटैशियम डाइक्रोमेट प्राप्त कर लिया जाता है। Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl पोटैशियम डाइक्रोमेट के नारंगी रंग के क्रिस्टल, क्रिस्टलीकृत हो जाते हैं। जलीय विलयन में क्रोमेट तथा डाइक्रोमेट का अन्तरारूपान्तरण होता है जो विलयन के pH पर निर्भर करता है। क्रोमेट तथा डाइक्रोमेट में क्रोमियम की ऑक्सीकरण संख्या समान है। 2CrO^2-₄ + 2H⁺ → Cr₂O^2-₇+ H₂O Cr₂O^2-₇ + 2OH^– → 2CrO^2-₄ + H₂O अत: pH बढ़ाने पर, अर्थात् विलयन को क्षारीय करने पर, डाइक्रोमेट आयन (नारंगी रंग) क्रोमेट आयनों में परिवर्तित हो जाते हैं तथा विलयन का रंग पीला हो जाता है।

16.

आयरन क्रोमाइट अयस्क से पोटैशियम डाइक्रोमेट बनाने की विधि का वर्णन कीजिए। पोटैशियम डाइक्रोमेट विलयन पर pH बढ़ाने से क्या प्रभाव पड़ेगा?

Answer»

पोटैशियम डाइक्रोमेट बनाने की विधि (Method of Preparation of Potassium Dichromate) – आयरन क्रोमाइट अयस्क (FeCr₂O₄) को जब वायु की उपस्थिति में सोडियम यो पोटैशियम कार्बोनेट के साथ संगलित किया जाता है तो क्रोमेट प्राप्त होता है।

4FeCr₂O₄ + 8Na₂CO₃ + 7O₂ → 8Na₂CrO₄ +2Fe₂O₃ + 8CO₂ ↑

सोडियम क्रोमेट के पीले विलयन को छानकर उसे सल्फ्यूरिक अम्ल द्वारा अम्लीय बना लिया जाता है। जिसमें से नारंगी सोडियम डाइक्रोमेट, Na₂Cr₂O₇ . 2H₂O को क्रिस्टलित कर लिया जाता है।

2Na₂CrO₄ + 2H⁺ → Na₂Cr₂O₇ + 2Na⁺ + H₂O

सोडियम डाइक्रोमेट की विलेयता, पोटैशियम डाइक्रोमेट से अधिक होती है, इसलिए सोडियम डाइक्रोमेट के विलयन में पोटैशियम क्लोराइड डालकर पोटैशियम डाइक्रोमेट प्राप्त कर लिया जाता है।

Na2Cr2O7 + 2KCl → K2Cr2O7 + 2NaCl

पोटैशियम डाइक्रोमेट के नारंगी रंग के क्रिस्टल, क्रिस्टलीकृत हो जाते हैं। जलीय विलयन में क्रोमेट तथा डाइक्रोमेट का अन्तरारूपान्तरण होता है जो विलयन के pH पर निर्भर करता है। क्रोमेट तथा डाइक्रोमेट में क्रोमियम की ऑक्सीकरण संख्या समान है।

2CrO^2-₄ + 2H⁺ → Cr₂O^2-₇+ H₂O

Cr₂O^2-₇ + 2OH^– → 2CrO^2-₄ + H₂O

अत: pH बढ़ाने पर, अर्थात् विलयन को क्षारीय करने पर, डाइक्रोमेट आयन (नारंगी रंग) क्रोमेट आयनों में परिवर्तित हो जाते हैं तथा विलयन का रंग पीला हो जाता है।

Discussion

17.	61, 91, 101 तथा 109 परमाणु क्रमांक वाले तत्वों का इलेक्ट्रॉनिक विन्यास लिखिए।
Answer» Z = 61 (प्रोमिथियम, Pr) का इलेक्ट्रॉनिक विन्यास, [Xe]⁵⁴ 4f⁵ 5d⁰ 6s² Z = 91 (प्रोटेक्टिनियम, Pa) का इलेक्ट्रॉनिक विन्यास, [Rn]⁸⁶ 5f²6d¹ 7s² Z = 101 (मेण्डेलीवियम, Md) का इलेक्ट्रॉनिक विन्यास [Rn]⁸⁶ 5f¹³ 6d0 7s² Z = 109 (मेटनेरियम, Mt) का इलेक्ट्रॉनिक विन्यास [Rn]⁸⁶ 5f¹⁴ 6d⁷ 7s²

17.

61, 91, 101 तथा 109 परमाणु क्रमांक वाले तत्वों का इलेक्ट्रॉनिक विन्यास लिखिए।

Answer»

Z = 61 (प्रोमिथियम, Pr) का इलेक्ट्रॉनिक विन्यास,

[Xe]⁵⁴ 4f⁵ 5d⁰ 6s²

Z = 91 (प्रोटेक्टिनियम, Pa) का इलेक्ट्रॉनिक विन्यास,

[Rn]⁸⁶ 5f²6d¹ 7s²

Z = 101 (मेण्डेलीवियम, Md) का इलेक्ट्रॉनिक विन्यास

[Rn]⁸⁶ 5f¹³ 6d0 7s²

Z = 109 (मेटनेरियम, Mt) का इलेक्ट्रॉनिक विन्यास

[Rn]⁸⁶ 5f¹⁴ 6d⁷ 7s²

Discussion

18.	In a dihybrid cross white eyed, yellow bodied female Drosophila crossed with red eyed, brown bodied male Drosophila produced in F2 generation, 1.3 per cent recombinants and 98.7 per cent progeny with parental type combinations. This observation of Morgan deviated from Mendelian F2 phenotypic dihybrid ratio. Explain, giving reasons, Morgan’s observations.
Answer» Morgan saw that when the two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than the non-parental type. Morgan attributed this due to physical association or linkage of two genes and coined the term linkage to describe this physical association of genes on a chromosome and the term recombination to describe the generation of nonparental gene combinations.

Discussion

19.	What is lanthanide contraction? What effect does it have on the chemistry of the elements, which follow lanthanoids?
Answer» The size of Lanthanoids and its trivalent ion decreases from La to Lu. It is known as lanthanoids contraction. Cause: It is due to poor shielding of 4f electrons. Consequences of lanthanide contraction: (i) Basic strength of hydroxide decreases from La(OH)₃ TO Lu(OH)₃. (ii) Because of similar chemical properties lanthanides are difficult to separate.

19.

What is lanthanide contraction? What effect does it have on the chemistry of the elements, which follow lanthanoids?

Answer»

The size of Lanthanoids and its trivalent ion decreases from La to Lu. It is known as lanthanoids contraction.

Cause: It is due to poor shielding of 4f electrons. Consequences of lanthanide contraction:

(i) Basic strength of hydroxide decreases from La(OH)₃ TO Lu(OH)₃.

(ii) Because of similar chemical properties lanthanides are difficult to separate.

Discussion

20.	What is lanthanide contraction? How does it affect the chemistry of elements, which follow lanthanoids?
Answer» Decrease in atomic/ionic radii across lanthanoid series with increase in atomic number. Due to lanthanoid contration the atomic/ionic radii 5 d Series elements decrease Consequently the properties of 4 d and 5 d series elements become similar.

20.

What is lanthanide contraction? How does it affect the chemistry of elements, which follow lanthanoids?

Answer»

Decrease in atomic/ionic radii across lanthanoid series with increase in atomic number.

Due to lanthanoid contration the atomic/ionic radii 5 d Series elements decrease Consequently the properties of 4 d and 5 d series elements become similar.

Discussion

21.	Define Boyle temperature or Boyle point.
Answer» The temperature at which a real gas obeys ideal gas laws over an appreciable range of pressure is called Boyle temperature or Boyle point.

Discussion

22.	Assertion: Though the central atom of both NH3 and H2O molecules are sp3 hybridized , yet H-N-H bond angle is greater than that of H-O-H.Reason: this is because nitrogen atom has one lone pair and oxygen atom has two lone pair(a) If both A & R are correct and R is the correct explanation of the assertion.(b) If both A & R are correct but R is not the correct explanation of the assertion.(c) If A is correct ,but R is incorrect(d) If both A & R are incorrect
Answer» (a) If both A & R are correct and R is the correct explanation of the assertion.

Discussion

23.	8 g of methane is placed in 5 litre container at 270C. Find Boyle constant.
Answer» PV= Boyle Constant But PV= nRT =w/M RT =8/16 mol x 0.0821L atm K^-1 mol^-1 x 300 k = 12.315 L atm Hence, Boyle constant= 12.315 L atm

23.

8 g of methane is placed in 5 litre container at 270C. Find Boyle constant.

Answer»

PV= Boyle Constant

But PV= nRT =w/M RT

=8/16 mol x 0.0821L atm K^-1 mol^-1 x 300 k

= 12.315 L atm

Hence, Boyle constant= 12.315 L atm

Discussion

24.	Which one of the following is not a property of carbona) It exhibits catenationb) It forms multiple bondsc) Its melting point and boiling points are very highd) It is a semi-metal
Answer» (d) Carbon is non metal

Discussion

25.	Assertion : BF3 molecule is planar but NF3 is notReason : N atom is smaller than B(a) If both A & R are correct and R is the correct explanation of the assertion.(b) If both A & R are correct but R is not the correct explanation of the assertion.(c) If A is correct ,but R is incorrect(d) If both A & R are incorrect
Answer» (b) If both A & R are correct but R is not the correct explanation of the assertion.

Discussion

26.	NF3 is an exothermic compound but NCl3 is not,Give reasons.
Answer» NF₃hydrolyse easily hence NF₃is highly exothermic.

Discussion

27.	Which of the following is the most ionic?a) CCl4b) SbCl4c) PbCl4d) SbCl2
Answer» (d) In group 14 oxidation state give ionic compounds while +4 oxidation states gives covalent compounds

Discussion

28.	Carbon and Silicon are mainly tetravalent but Ge, Sn and Pb show divalency. Give reason.
Answer» Ge, Sn, Pb are divalent due to inert pair effect which is not there in carbon and silicon.

Discussion

29.	CCl4 does not show hydrolysis but SiCl4 is readily hydrolyzed becausea) Carbon cannot expand its octet but silicon can expandb) Electronegativity of carbon is higher than siliconc) Ionization energy of carbon is higher than of silicond) Carbon form double and triple bonds but not silicon
Answer» a) Carbon cannot expand its octet but silicon can expand

Discussion

30.	PbCl4 is less stable than SnCl4 but PbCl2 is more stable than SnCl2. Justify?
Answer» due to inert pair effect +4 valency is less stable than +2 in case of Pb.

Discussion

31.	Write one similarity and one difference between the chemistry of lanthanoids and actinoids?
Answer» Similarity : (i) Both show contraction in size. (ii) Both show irregularity in their electronic configuration (iii) Both are stable in + 3 oxidation state. (Any one) Difference : (i) Actinoids are mainly radioactive but lanthanoids are not (ii) Actinoids show wide range of oxidation states but lanthanoids do not (iii) Actinoid contraction is greater than lanthanoid contraction. (any other one similarity and one difference.

31.

Write one similarity and one difference between the chemistry of lanthanoids and actinoids?

Answer»

Similarity : (i) Both show contraction in size. (ii) Both show irregularity in their electronic configuration (iii) Both are stable in + 3 oxidation state. (Any one)

Difference : (i) Actinoids are mainly radioactive but lanthanoids are not (ii) Actinoids show wide range of oxidation states but lanthanoids do not

(iii) Actinoid contraction is greater than lanthanoid contraction. (any other one similarity and one difference.

Discussion

32.	Suggest reasons for the following features of transition metal chemistry :(i) The transition metals and their compounds are usually paramagnetic.(ii) The transition metals exhibit variable oxidation states.
Answer» (i) Due to presence of unpaired electrons in d-orbitals. (ii) Due to incomplete filling of d- orbitals.Due to very small energy difference in between (n-1)d and n s - orbitals.

32.

Suggest reasons for the following features of transition metal chemistry :(i) The transition metals and their compounds are usually paramagnetic.(ii) The transition metals exhibit variable oxidation states.

Answer»

(i) Due to presence of unpaired electrons in d-orbitals.

(ii) Due to incomplete filling of d- orbitals.Due to very small energy difference in between (n-1)d and n s - orbitals.

Discussion

33.	The compound (X) on heating gives a colourless gas and a residue that is dissolved in water to obtain (B). Excess of CO2 is bubbled through aqueous solution of B, C is formed. Solid (C) on heating gives back X. (B) is ……(a) CaCO3 (b) Ca(OH)2 (c) Na2CO3 (d) NaHCO3
Answer» (b) Ca(OH)₂ CaCO₃\(\overset{\Delta}{\longrightarrow}\) CaO + CO₂ CaO + H₂O → Ca(OH)₂ Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

33.

The compound (X) on heating gives a colourless gas and a residue that is dissolved in water to obtain (B). Excess of CO2 is bubbled through aqueous solution of B, C is formed. Solid (C) on heating gives back X. (B) is ……(a) CaCO3 (b) Ca(OH)2 (c) Na2CO3 (d) NaHCO3

Answer»

(b) Ca(OH)₂

CaCO₃\(\overset{\Delta}{\longrightarrow}\) CaO + CO₂

CaO + H₂O → Ca(OH)₂

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Discussion

34.	The hydroxides and carbonates of sodium and potassium are easily soluble in water, while the corresponding salts of magnesium and calcium are sparingly soluble in water. Explain
Answer» All the compounds are crystalline solids and their solubility in water is guided by both lattice enthalpy and hydration enthalpy. The magnitude of lattice enthalpy is quite small in case of sodium and potassium compounds, hence they are readily dissolved in water, when compared to magnesium and calcium compounds. However, in case of corresponding magnesium and calcium compounds, the cations have smaller sizes and more magnitude of positive charge. This means that their lattice enthalpies are more, when compared to the sodium and potassium compounds. Therefore, the hydroxi des and carbonates of these metals are only sparingly soluble in water.

34.

The hydroxides and carbonates of sodium and potassium are easily soluble in water, while the corresponding salts of magnesium and calcium are sparingly soluble in water. Explain

Answer»

All the compounds are crystalline solids and their solubility in water is guided by both lattice enthalpy and hydration enthalpy. The magnitude of lattice enthalpy is quite small in case of sodium and potassium compounds, hence they are readily dissolved in water, when compared to magnesium and calcium compounds.

However, in case of corresponding magnesium and calcium compounds, the cations have smaller sizes and more magnitude of positive charge. This means that their lattice enthalpies are more, when compared to the sodium and potassium compounds.

Therefore, the hydroxi des and carbonates of these metals are only sparingly soluble in water.

Discussion

35.	Although Cr3+ and Co2+ ions have same number of unpaired electrons but the magnetic moment of Cr3+ is 3.87 B.M. and that of Co2+ is 4.87 B.M. Why?
Answer» Due to symmetrical electronic configuration there is no orbital contribution in Cr³⁺ ion. However appreciable orbital contribution takes place in Co²⁺ion.

Discussion

36.	A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should the impurity belong?
Answer» n-type semiconductor means conduction due to presence of excess of negatively charged electrons. Hence to convert group 14 element into n-type semiconductor, it should be doped with group 15 element.

Discussion

37.	निम्नलिखित अभिक्रियाओं के वेग व्यंजकों से इनकी अभिक्रिया कोटि तथा वेग स्थिरांकों की इकाइयाँ ज्ञात कीजिए – 1. 3NO (g) → N2O (g) वेग = k [NO]2 2. H2O2 (aq) + 3I– (aq) + 2H+ → 2H2O(l) + I–3 वेग = k [H2O2] [I–] 3. CH3CHO (g) → CH4 (g)+ CO (g) वेग = k [CH3CHO]3/2 4. C2H5Cl (g) → C2H4 (g) + HCl (g) वेग = k [C2H5Cl]
Answer» 1. द्वितीय कोटि,L mol^-1 time^-1 2. farite alfa, L mol^-1 time^-1 3. 3/2 कोटि, L^1/2 mol^-1/2 time^-1 4. प्रथम कोटि, time^-1

37.

निम्नलिखित अभिक्रियाओं के वेग व्यंजकों से इनकी अभिक्रिया कोटि तथा वेग स्थिरांकों की इकाइयाँ ज्ञात कीजिए – 1. 3NO (g) → N2O (g) वेग = k [NO]2 2. H2O2 (aq) + 3I– (aq) + 2H+ → 2H2O(l) + I–3 वेग = k [H2O2] [I–] 3. CH3CHO (g) → CH4 (g)+ CO (g) वेग = k [CH3CHO]3/2 4. C2H5Cl (g) → C2H4 (g) + HCl (g) वेग = k [C2H5Cl]

Answer»

1. द्वितीय कोटि,L mol^-1 time^-1

2. farite alfa, L mol^-1 time^-1

3. 3/2 कोटि, L^1/2 mol^-1/2 time^-1

4. प्रथम कोटि, time^-1

Discussion

38.	Which one of the following is correct order of the stability of carbanions?(a) -C(CH3)3 > -CH(CH3)2 > -CH2 -CH3 > -CH3 (b) -CH3 > -CH2 -CH3 > -CH(CH3)2 > -C(CH3)3 (c) -CH(CH3), > -CH3 > -CH2 -CH3 > -C(CH3)3 (d) -CH2 -CH3 > -CH(CH3)2 > -CH3 > -C(CH3)3
Answer» (b) ^-CH₃ > ^-CH₂ -CH₃ > ^-CH(CH₃)₂ > ^-C(CH₃)₃

Discussion

39.	Which of the following carbocation will be most stable? (a) PH3C+ - (b) CH3 - C+H2 (c) (CH3)2 - C+H (d) CH2 = CH - CH3
Answer» Correct answer is (a) PH₃C⁺-

Discussion

40.	Which one of the following has strongest acidic character? (a) HCOOH (b) CH3COOH (c) CH2ClCOOH (d) CCl3COOH
Answer» Correct answer is (d) CCl₃COOH

Discussion

41.

Match the following List - IList - IIA. Addition reaction1. NtrationB. Elimination reaction 2. HydrationC. Ncleophilic substitution3. DehydrationD. Electrophilic substitution4.Hydrolysis of alkyl halides Code :ABCD(a)1234(b)4321(c)2341(d)3421

Answer»

	A	B	C	D
(c)	2	3	4	1

Discussion

42.	Choose the correct pair(a) CH3 – CH2 – CH2Br + Alcoholic KOH : Substitution reaction (b) CH3 – CH2 – CH2Br + Alcoholic KOH : Elimination reaction (c) CH3CHO + Acidic dichromate : Reduction reaction (d) Benzene + Pt + H2 : Oxidation reaction
Answer» (b) CH₃ – CH₂ – CH₂Br + Alcoholic KOH : Elimination reaction

Discussion

43.	CH3CHO \(\overset {(O)}{\longrightarrow}\) CH3COOH Identify the type of reaction(a) Addition reaction (b) Elimination reaction (c) Reduction reaction (d) Oxidation reaction
Answer» (d) Oxidation reaction

Discussion

44.	Which of the following species does not exert a resonance effect?(a) C6H5OH (b) C6H5Cl (c) C6H5NH2(d) C6H5NH3
Answer» Correct answer is (d) C₆H₅NH₃

Discussion

45.	Primary alcohols undergo which type of reaction to form alkenes? (a) Elimination (b) Oxidation (c) Reduction (d) Hydrolysis
Answer» Correct answer is (a) Elimination

Discussion

46.	Choose the odd one out (a) -OH (b) -NH2 (c) -SH (d) -COOH
Answer» (d) – COOH. It has negative mesomeric effect whereas others have positive mesomeric effect.

46.

Choose the odd one out (a) -OH (b) -NH2 (c) -SH (d) -COOH

Answer»

(d) – COOH.

It has negative mesomeric effect whereas others have positive mesomeric effect.

Discussion

47.	Choose the incorrect pair (a) NH3 andAmines : Neutral nucleophile (b) OH- and RCOO- : Negative nucleophile (c) RX and H3O3 : Positive electrophile (d) MCl3 , BF3 : Negative electrophile
Answer» (d) AlCl₃ , BF₃ : Negative electrophile

Discussion

48.	Which one of the following electrophile used for nitration of benzene?(a) Br⊕(b) NO2⊖(c) -NH2(d) NO⊖
Answer» Correct answer is (b) NO₂^⊖

Discussion

49.	Assertion (A): Phenol is more acidic than aliphatic alcohols.Reason (R): The phenoxide ion is more stabilized than phenol by resonance effect and hence resonance favours ionization of phenol to form H and shows acidity. (a) Both (A) and (R) are correct and (R) is the correct explanation of(A). (b) Both (A) and (R) are correct but (R) is not the correct explanation of(A). (c) (A) is correct but (R) is wrong. (d) (A) is wrong but (R) is correct.
Answer» (a) Both (A) and (R) are correct and (R) is the correct explanation of(A).

Discussion

50.	Decreasing order of nucleophilicity is – (a) OH- > RNH2- > -OCH3 > RNH2 (b) NH2- > OH- > -OCH3 > RNH2 (c) NH,> CH3O >OH- > RNH2 (d) CH3O- > NH2- > OH- > RNH2
Answer» (b) NH₂^- > OH^- > OCH₃ > RNH₂

Discussion

Explore topic-wise InterviewSolutions in Current Affairs.

Who are the main contributors of modem : synthetic theory of evolution?

Describe in brief the palaeontological evidences of human evolution.

Explain modern synthetic theory of evolution.

Which statement is true for the theory of spontaneous generation? (a) Life came from outer space. (b) Life can arise from dead matter. (c) Life can arise from non-living things only (d) Life arises spontaneously by miracle

What is abiogenesis? Explain the ‘Theory of spontaneous generation’ or ‘Theory of abiogenesis’.

Who conducted experiment to verify Oparin’s theory about creation?(a) Haldane(b) Jagdish Chandra Bose(c) Birbal Sahni(d) Miller

Give the three key factors of the modern synthetic theory of evolution.

Haldane described ‘Hot dilute soup’ in his theory. Describe how this soup led to formation of some important molecules.

Oparin’s theory is based on(A) artificial synthesis(B) spontaneous generation(C) will of God(D) all of these

Explain modern Synthetic Theory of Evolution in brief.

Theory of special creation is based on ………………. beliefs. (a) scientific(b) religious (c) traditional (d) mythological

The human chromosome with highest and least number of gene is: A) Chromosome 21 and Y B) Chromosome 1 and X C) Chromosome 1 and Y D) Chromosome X and Y

Variations during mutations of meiotic recombinations are ………………. (a) random and directionless (b) random and directional (c) small and directional (d) random, small and directional

Industrial melanism observed in moth, Biston bitularia shows ………………. type of natural selection. (a) stabilising (b) directional (c) disruptive (d) artificial

Why does the hnRNA need to undergo changes ? List the changes hnRNA undergoes and where in the cell such changes take place.

61, 91, 101 तथा 109 परमाणु क्रमांक वाले तत्वों का इलेक्ट्रॉनिक विन्यास लिखिए।

What is lanthanide contraction? What effect does it have on the chemistry of the elements, which follow lanthanoids?

What is lanthanide contraction? How does it affect the chemistry of elements, which follow lanthanoids?

Define Boyle temperature or Boyle point.

8 g of methane is placed in 5 litre container at 270C. Find Boyle constant.

Which one of the following is not a property of carbona) It exhibits catenationb) It forms multiple bondsc) Its melting point and boiling points are very highd) It is a semi-metal

NF3 is an exothermic compound but NCl3 is not,Give reasons.

Which of the following is the most ionic?a) CCl4b) SbCl4c) PbCl4d) SbCl2

Carbon and Silicon are mainly tetravalent but Ge, Sn and Pb show divalency. Give reason.

CCl4 does not show hydrolysis but SiCl4 is readily hydrolyzed becausea) Carbon cannot expand its octet but silicon can expandb) Electronegativity of carbon is higher than siliconc) Ionization energy of carbon is higher than of silicond) Carbon form double and triple bonds but not silicon

PbCl4 is less stable than SnCl4 but PbCl2 is more stable than SnCl2. Justify?

Write one similarity and one difference between the chemistry of lanthanoids and actinoids?

Suggest reasons for the following features of transition metal chemistry :(i) The transition metals and their compounds are usually paramagnetic.(ii) The transition metals exhibit variable oxidation states.

The compound (X) on heating gives a colourless gas and a residue that is dissolved in water to obtain (B). Excess of CO2 is bubbled through aqueous solution of B, C is formed. Solid (C) on heating gives back X. (B) is ……(a) CaCO3 (b) Ca(OH)2 (c) Na2CO3 (d) NaHCO3

The hydroxides and carbonates of sodium and potassium are easily soluble in water, while the corresponding salts of magnesium and calcium are sparingly soluble in water. Explain

Although Cr3+ and Co2+ ions have same number of unpaired electrons but the magnetic moment of Cr3+ is 3.87 B.M. and that of Co2+ is 4.87 B.M. Why?

A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should the impurity belong?

Which one of the following is correct order of the stability of carbanions?(a) -C(CH3)3 &gt; -CH(CH3)2 &gt; -CH2 -CH3 &gt; -CH3 (b) -CH3 &gt; -CH2 -CH3 &gt; -CH(CH3)2 &gt; -C(CH3)3 (c) -CH(CH3), &gt; -CH3 &gt; -CH2 -CH3 &gt; -C(CH3)3 (d) -CH2 -CH3 &gt; -CH(CH3)2 &gt; -CH3 &gt; -C(CH3)3

Which of the following carbocation will be most stable? (a) PH3C+ - (b) CH3 - C+H2 (c) (CH3)2 - C+H (d) CH2 = CH - CH3

Which one of the following has strongest acidic character? (a) HCOOH (b) CH3COOH (c) CH2ClCOOH (d) CCl3COOH

Match the following List - IList - IIA. Addition reaction1. NtrationB. Elimination reaction 2. HydrationC. Ncleophilic substitution3. DehydrationD. Electrophilic substitution4.Hydrolysis of alkyl halides Code :ABCD(a)1234(b)4321(c)2341(d)3421

Choose the correct pair(a) CH3 – CH2 – CH2Br + Alcoholic KOH : Substitution reaction (b) CH3 – CH2 – CH2Br + Alcoholic KOH : Elimination reaction (c) CH3CHO + Acidic dichromate : Reduction reaction (d) Benzene + Pt + H2 : Oxidation reaction

CH3CHO \(\overset {(O)}{\longrightarrow}\) CH3COOH Identify the type of reaction(a) Addition reaction (b) Elimination reaction (c) Reduction reaction (d) Oxidation reaction

Which of the following species does not exert a resonance effect?(a) C6H5OH (b) C6H5Cl (c) C6H5NH2(d) C6H5NH3

Primary alcohols undergo which type of reaction to form alkenes? (a) Elimination (b) Oxidation (c) Reduction (d) Hydrolysis

Choose the odd one out (a) -OH (b) -NH2 (c) -SH (d) -COOH

Choose the incorrect pair (a) NH3 andAmines : Neutral nucleophile (b) OH- and RCOO- : Negative nucleophile (c) RX and H3O3 : Positive electrophile (d) MCl3 , BF3 : Negative electrophile

Which one of the following electrophile used for nitration of benzene?(a) Br⊕(b) NO2⊖(c) -NH2(d) NO⊖

Decreasing order of nucleophilicity is – (a) OH- &gt; RNH2- &gt; -OCH3 &gt; RNH2 (b) NH2- &gt; OH- &gt; -OCH3 &gt; RNH2 (c) NH,&gt; CH3O &gt;OH- &gt; RNH2 (d) CH3O- &gt; NH2- &gt; OH- &gt; RNH2

Which one of the following is correct order of the stability of carbanions?(a) -C(CH3)3 > -CH(CH3)2 > -CH2 -CH3 > -CH3 (b) -CH3 > -CH2 -CH3 > -CH(CH3)2 > -C(CH3)3 (c) -CH(CH3), > -CH3 > -CH2 -CH3 > -C(CH3)3 (d) -CH2 -CH3 > -CH(CH3)2 > -CH3 > -C(CH3)3

Decreasing order of nucleophilicity is – (a) OH- > RNH2- > -OCH3 > RNH2 (b) NH2- > OH- > -OCH3 > RNH2 (c) NH,> CH3O >OH- > RNH2 (d) CH3O- > NH2- > OH- > RNH2