Explore topic-wise InterviewSolutions in Current Affairs.

This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.

1.

Why partial roasting of sulphide ore is done in the metallurgy of copper ?A. Auto-reduction of `Cu_(2)O` formed is carried out by remaining `Cu_(2)S` in the reaction.B. Cu is separated out by partial reduction due to sedimentationC. Due to difference in gravity `Cu_(2)O` and `Cu_(2)S` are separated.D. Complete roasting cannot be done in one step hence partial roasting is done.

Answer» Correct Answer - A
Partial roasting of sulphide ore forms some oxide. This oxide then reduces the remaining sulphide ore into metal.
`2Cu_(2)S + 3O_(2) to 2Cu_(2)O + 2SO_(2)`
`2Cu_(2)O + Cu_(2)S to 6Cu + SO_(2)`
This process is called autoreduction.
2.

Blister copper isA. impure copperB. obtained in self-reduction process during bessemerisationC. both are correctD. none is correct

Answer» Correct Answer - C
Blister copper is impure copper obtained in self reduction process during bessemerisation .
3.

In the extraction of gold, the cyanide solution acts as aA. leaching agent that dissolves the impuritiesB. FluxC. leaching agent that acts a complex forming reactantD. reducing agent that converts the metal oxide or sulphide into the metal

Answer» Correct Answer - C
When the gold pass into the solution of sodium or potassium cyanide forming the respective soluble complex cyanides while the impurities remain unaffected which are filtered off.
`4Au+8KCN+O_(2)+2H_(2)Orarr underset("Pot.dicyanoaurate(I) (solubl e compl ex"))(4K[Au(CN)_(2)]+4KOH`
4.

Silica is added to the sulphide ore of copper in reverberatory furnace becauseA. sulphide ore of copper contains iron as impurity which is removed as iron slag.B. silica reacts with `Cu_(2)O` to form slagC. silica helps in reduction of `Cu_(2)O ` to CuD. sulphide ore of copper is separated from iron by reacting with silica.

Answer» Correct Answer - A
The impurities of iron present with copper are removed as iron silicate.
`FeO + SiO_(2) to underset("Slag")(FeSiO_(3))`
5.

Statement-1:In cyanide process for the extraction of gold and silver from their native ores, the cyanide solution acts as a reducing agent to reduce the gold and silver compounds present in the ores, the cyanide solution acts as a reducing agent to reduce the gold and silver compounds present in the ores into the metallic states. Statement-2:In the extraction of gold and silver the cyanide solution acts as complexing reagent in the presence of air and form their respective soluble complexes.A. Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement-1B. Statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1C. Statement-1 is True, Statement-2 is False.D. Statement-1 is False, Statement-2 is True.

Answer» Correct Answer - D
Statement -1 : 4M(s)+`8CN^(-)(aq)+O_2(g)to overset(+I)(4[M(CN)_2]^(-)(aq)+4OH^(-)(aq).` M=Au or Ag. As it is clear from the equation that `CN^(-)` does not acts as reducing agent However `O_2` oxidies metal to metal ion which then react with `CN^(-)` ion to form complex from which metal is obtained by reduction by more electropositive metal, zinc,.
Statement-2:`4M(s)+8CN^(-)(aq.)+2H_2O(aq)+O_2(g)to overset(+I)(4[M(CN)_2]^(-)(aq)+4OH^(-)(aq).` M=Au or Ag.
6.

`A overset("Calcination")rarr CaO + MgO + underset("Colourless gas")((B))` When the colourless gas `(B)` is passed through lime water, initially a milky solution is obtained and on excess passage of gas `(B)` through the lime water, milkiness disappears. Lime water is.A. `CaO`B. `CA(OH)_(2)`C. `CaCO_(3)`D. `CaCO_(3) .Ca(OH)_(2)`

Answer» Correct Answer - B
Since on calcination, i.e., heating the ore `(A)` is limited supply of `O_(2)`, both `CaO` and `MgO` are formed along with a colourless gas `(B). (A)` is `CaCO_(3).MgCO_(3).(A)` is known as dolomite.
`CaCO_(3).MgCO_(3) overset("Calcination")rarr CaO + MgO + underset((B))(2CO_(2))`
`CO_(2) + underset("Lime water")(Ca(OH)_(2))rarr underset("Milkiness") (CaCO_(3))+ H_(2) O`
`CaCO_(3) +H_(2) O + CO_(2) rarr underset("Milkiness disappears") (Ca(HCO_(3))_(2))`
On passing `CO_(2)` through lime water `[Ca(OH)_(2)]` solution, initially lime water turns milky due to formation of `CaCo_(3)`, which is insoluble in water. On excess passage of `CO_(2)` gas through lime water, milkiness disppears due to formation of `Ca(HCO_(3))_(2)`. Hence.
(iv) Limewater is `Ca(OH)_(2)` solution.
7.

`A overset("Calcination")rarr CaO + MgO + underset("Colourless gas")((B))` When the colourless gas `(B)` is passed through lime water, initially a milky solution is obtained and on excess passage of gas `(B)` through the lime water, milkiness disappears. Milkiness of lime water solution disappears due to the formation of :A. `CaCO_(3)`B. `Ca(HCO_(3))_(2)`C. `Ca(OH)_(2)`D. `CaCl_(2)`

Answer» Correct Answer - B
Since on calcination, i.e., heating the ore `(A)` is limited supply of `O_(2)`, both `CaO` and `MgO` are formed along with a colourless gas `(B). (A)` is `CaCO_(3).MgCO_(3).(A)` is known as dolomite.
`CaCO_(3).MgCO_(3) overset("Calcination")rarr CaO + MgO + underset((B))(2CO_(2))`
`CO_(2) + underset("Lime water")(Ca(OH)_(2))rarr underset("Milkiness") (CaCO_(3))+ H_(2) O`
`CaCO_(3) +H_(2) O + CO_(2) rarr underset("Milkiness disappears") (Ca(HCO_(3))_(2))`
On passing `CO_(2)` through lime water `[Ca(OH)_(2)]` solution, initially lime water turns milky due to formation of `CaCo_(3)`, which is insoluble in water. On excess passage of `CO_(2)` gas through lime water, milkiness disppears due to formation of `Ca(HCO_(3))_(2)`. Hence.
(v) Milkiness disappears due to formation of `Ca(HCO_(3))_(2)`.
8.

Assertion: Silica is added as a flux in reverberatory furnace, in the extrcation of copper from copper phyrites. Reason: Silica decreases the melting point of the ore and increases the conductivity.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is false.D. If assertion is false but reason is true.

Answer» Correct Answer - C
Assertion: `FeO +SiO_(2)rarr FeSiO_(3)`.
Reason: Reason is incorrect as `SiO_(2)` is a covalent compound and thus does not ionise to give ions responsible for conducting the electric current.
9.

Statement-1:Silica is added as a flux in reverberatory furnace, in the extraction of copper from copper pyrites. Statement-2:Silica acts as basic flux.A. Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement-1B. Statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1C. Statement-1 is True, Statement-2 is False.D. Statement-1 is False, Statement-2 is True.

Answer» Correct Answer - C
`S_1:2CuFeS_2+O_2toCu_2S+2FeS+SO_2`,
`2FeS+3O_2 to 2FeO +2SO_2`
`FeO+SiO_2 to FeSiO_3`, thus remove the basic impurity of iron oxide.
`S_2`:Silica acts as an acidic flux.
10.

Which of the following statement is incorrect ?A. Electrostatic separation is used for lead sulphideB. Galena is an ore of PbC. Ore is heated strongly above its melting point in roastingD. Silica acts as acidic flux

Answer» Correct Answer - C
Roasting is the process in which the ore is heated strongly below its melting point in the presence of air.
11.

Which of the following is not an ore of magnesium ?A. CarnalliteB. DolomiteC. CalamineD. Sea water.

Answer» Correct Answer - C
Calamine `(ZnCO_(3))` is the ore of zinc metal.
12.

Sulphide ores of metals are usually concentrated by both floatation process. Which of the following sulphide ores offers an exception and is concentrated by chemical leaching ?A. ArgentiteB. GalenaC. Copper pyriteD. Sphalerite

Answer» Correct Answer - D
Galena (PbS), copper pyrite `(CuFeS_2)` and argentite `(Ag_2S)` are concentrated by froth floatation process but sphalerite (ZnS) is concentrated by chemical leaching .
13.

Sulphide ores of the metals are usually concentrated by froth floatation process. Which of the following sulphide ores offers an exception and is concentrated by chemical leaching ?A. GalenaB. Copper pyriteC. SphaleriteD. Argentite.

Answer» Correct Answer - D
Argentite `(Ag_(2)S)` an ore of silver metal is concentrated by the leaching and the process is known as Mac-Arthur and Forest process.
14.

Which of the following statements is not correct ?A. Zinc can be extracted from its ore by roasting followed by reduction with coke.B. In reverberatory furnace , both oxidation and reduction processes can be carrried out.C. Silver is purifed by distillation or liquation process.D. Highly pure metals are obtained by zone refining.

Answer» Correct Answer - C
Liquation or distillation is used for purification of metal with low boiling or melting point.
15.

Extraction of zinc from zinc blende is achieved byA. electrolyte reductionB. roasting followed by reduction with carbonC. roasting followed by reduction with another metalD. roasting followed by self reduction

Answer» Correct Answer - B
Extraction involves roasting followed by reduction with carbon.
16.

Find the incorrect match.A. Fine dust of aluminium - Paints and LacquersB. Reducing agent in the manufacture of dye-stuffs,paints etc.-Copper dustC. For cutting tools and crushing machines -Chorme steelD. For making cables, automobiles and aeroplane parts -Nickel steel

Answer» Correct Answer - B
Zinc dust is used as a reducing agent in the manufacture of dye-stuffs, paints, etc.
17.

___________ and ________ are alloys of copper.A. Brass and BronzeB. Brass and alloy steelC. Copper pyrites and malachiteD. Copper glance and cuprite

Answer» Correct Answer - A
Brass is Cu+Zn and bronze is Cu+Sn.
18.

Which of the following statements about the advantage of roasting of sulphide ore before reduction is not true ?A. The `Delta G^(@)` of the sulphide is greater than those of `CS_(2) " and " H_(2)S`.B. The `DeltaG^(@)` is negative for roasting of sulphide ore to oxide.C. Roasting of sulphide to oxide is thermodynamically feasibleD. Carbon and hydrogen are not suitable reducing agents for metal sulphides.

Answer» Correct Answer - D
Both C and `H_(2)` are not suitable for reducing sulphide ore because `Delta_(f)G^(@)` of metal sulphide is more than that of `CS_(2) " and H_(2)S` which will be formed as result of redcution.
19.

Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true gtA. The `DeltaG_(f)^(@)` of the sulphide is greater than those for `CS_(2)` and `H_(2)S`B. The `DeltaG_(F)^(@)` is negative for roasting of sulphide ore to oxide.C. Roasting of the sulphide to the oxide is thermodynamically feasible.D. Carbon and hydrogen are suitable reducing agents for metal sulphides.

Answer» Correct Answer - D
The standard free energies of formation `(DeltaG_(f)^(@))` of most of the sulphides are more negative than those of `CS_(2)` and `H_(2)S`. Hence, neither carbon nor hydrogen can reduce metal sulphides to metal. The standard free energies of formation of oxides are much lower than those of `SO_(2)` . Therefore , oxidation of metal sulphides to metal oxides is thermodynamically favourable. Hence sulphide ore is roasted to the oxide before reduction.
20.

Select similarity between alkali metals and coinage metalsA. Both are required to store in organic solventB. Both have high solubility in pure liquid ammonia to produce blue soltuionC. Both can be extracted by aqueous salt electrolysisD. Both have same number of electron `(s)`in outermost shell

Answer» Correct Answer - D
Electronic configuration of alkali metals `= [N.G.]ns^(-1)`
Electronic configuration of coinage metal
`(Cu,Ag,Au)=[N.G.](n-1)d^(10)ns^(-1)`
21.

If the impurity in a metal has a greater affinity for oxygen and is more easily oxidised than the matel, then the purification of metal may be carried out by:A. cupellationB. electroytic refiningC. zone refiningD. poling

Answer» Correct Answer - A
Cupellation,`Pb`present in `Ag` is removed by cupellation.
`Pb+(1)/(2)O_(2)rarr PbOuarr`
Bacuase `Pb` ahs more affinity for oxygen as compared to `Ag`.
22.

Extraction of copper is done using copper pyrites. After roasting, the ore is mixed with silica and coke and then smelted in a blast furnace. The matte obtained from the blast furnace is charged into a silica-lined converter. Some silica is also added, and a hot air blast is blown into the mixture to obtain blister copper, which is purified by electrorefining. The chemical composition of the slag formed during smelting is.A. `CuSiO_(3)`B. `FeSiO_(3)`C. `CaSiO_(3)`D. `Cu_(2)O. SiO_(2)`

Answer» Correct Answer - B
`FeO + SiO_(2) rarr FeSiO_(3)`.
23.

Roasting is a process in which the ore (mostly sulphide) is heated strongly in the presence of excess of air. The heating should be done at a temperature below the melting point of the ore. Select of correct statement :A. Roasting removes easily oxidisable volatile impurities like arsenic as `As_(2) O_(3)`, antimony as `Sb_(2) O_(3)`, and sulphur as `SO_(2)`.B. The release of `SO_(2)` (in roasting process) has been a serious air pollution problem.C. In roasting process, if temperature is fairly low (about `500^@ C`) and the concentration of `SO_(2)` in the gaseous enviourment is more, sulphate may be produced, that is stable, and high temperature is needed to decompose it.D. All are correct

Answer» Correct Answer - D
All the options `a,b` and `c` are correct.
24.

Roasting is a process in which the ore (mostly sulphide) is heated strongly in the presence of excess of air. The heating should be done at a temperature below the melting point of the ore. `2PbS + 3O_(2) rarr A + 2SO_(2)` The name of `A` is.A. LithargeB. GalenaC. SesquioxideD. None of these

Answer» Correct Answer - A
`2PbS + 3O_(2) rarr underset((A))(2PbO) + 2SO_(2)`
Hence, `A` i.e. `PbO`, commonly known as litharge.
25.

Fill in the blanks in the sentences below with words from the box. You may use a word more than once. carbon    cause    fires    mother (i) Gandhiji’s life was devoted to the ________________ of justice and fair play. (ii) Have you insured your house against ______________? (iii) Diamond is nothing but ____________ in its pure form. (iv) If you put too much coal on the fire at once you will ______________ it. (v) Smoking is said to be the main _____________ of heart disease. (vi) When asked by an ambitious writer whether he should put some ___________ into his stories, Somerset Maugham murmured, “No, the other way round”. (vii) She is a _____________ copy of her mother. (viii) It is often difficult to _____________ a yawn when you listen to a long speech on the value of time

Answer»

(i) Gandhiji’s life was devoted to the cause of justice and fair play. 

(ii) Have you insured your house against fire? 

(iii) Diamond is nothing but carbon in its pure form. 

(iv) If you put too much coal on the fire at once you will smother it. 

(v) Smoking is said to be the main cause of heart disease. 

(vi) When asked by an ambitious writer whether he should put some fire into his stories, Somerset Maugham murmured, “No, the other way round”. 

(vii) She is a carbon copy of her mother. 

(viii) It is often difficult to smother a yawn when you listen to a long speech on the value of time.

26.

Use the words given in the box to fill in the blanks in the sentences below. across   along    past     through (i) The cat chased the mouse ____________ the lawn. (ii) We were not allowed to cross the frontier. So we drove _________ it as far as we could and came back happy. (iii) The horse went _______________ the winning post and had to be stopped with difficulty. (iv) It is not difficult to see ____________ your plan. Anyone can see your motive. (v) Go ____________ the yellow line, then turn left. You will reach the post office in five minutes

Answer»

(i) The cat chased the mouse across the lawn. 

(ii) We were not allowed to cross the frontier. So we drove along it as far as we could and came back happy. 

(iii) The horse went past the winning post and had to be stopped with difficulty. 

(iv) It is not difficult to see through your plan. Anyone can see your motive. 

(v) Go along the yellow line, then turn left. You will reach the post office in five minutes.

27.

One word is italicised in each sentence. Find its opposite in the box and fill in the blanks. spendings hut destroy subtract  increase (i) You were required to keep all the doors open,not ____________. (ii) PUPIL: What mark did I get in yesterday’s Maths test? TEACHER: You got what you get when you add five and five and ___________ ten from the total. (iii) Run four kilometres a day to preserve your health. Run a lot more to __________ it. (iv) If a doctor advises a lean and lanky patient to reduce his weight further, be sure he is doing it to _____________ his income.(v) The world is too much with us; late and soon, Gettingand ___________ we lay waste our powers.

Answer»

(i) You were required to keep all the doors open, not shut. 

(ii) PUPIL: What mark did I get in yesterday’s Maths test? 

TEACHER: You got what you get when you add five and five and subtract ten from the total. 

(iii) Run four kilometres a day to preserve your health. Run a lot more to destroy it. 

(iv) If a doctor advises a lean and lanky patient to reduce his weight further, be sure he is doing it to increase his income. 

(v) The world is too much with us; late and soon, Getting and spending we lay waste our powers.

28.

What are the three main ways in which a fire can be controlled or put out?

Answer»

 Fire can be controlled or put out by taking away one of the three things required for burning. The first way is to take away the fuel. If the fire has no fuel to feed on, no burning can take place. The second way is to prevent oxygen from reaching it. Small fires can be put out with a damp blanket or a sack. This stops oxygen from reaching the burning material. Sometimes carbon dioxide is used for extinguishing fire. 

The third way of putting out a fire is to remove the heat. If the temperature can be brought down below the flash point, the fuel stops burning. Blowing on a burning matchstick or a candle removes the hot air around the flame, bringing down its temperature below the flash point. Sometimes water is sprayed on a fire. It absorbs heat from the burning fuel and lowers the temperature. It also cuts off the supply of oxygen, and therefore, fire is extinguished.

29.

Early man was frightened of (a) lightning and volcanoes. (b) the damage caused by them. (c) fire

Answer» Early man was frightened of fire.
30.

Spraying water is not a good way of putting out an oil fire or an electrical fire. Why not?

Answer»

If water is sprayed onto an oil fire, then the oil will float to the top of the water and continue to burn. This can be very dangerous because water can flow quickly, carrying the burning oil with it and spreading the fire. In case of an electrical fire, the person spraying water might receive an electric shock and be killed. Therefore, spraying water is not a good way of putting out an oil fire or an electrical fire

31.

Mark the correct answer in each of the following. (a) Fire is energy. (b) Fire is heat and light. (c) Fire is the result of a chemical reaction.

Answer» (ii) Fire is the result of a chemical reaction.
32.

In what sense is it a “bad master”?

Answer»

It is a “bad master” because if it is not kept under control, it can prove very dangerous. Each year thousands of homes and shops are damaged by fire. Vast areas of forest are also destroyed and hundreds of people are killed or injured.

33.

From the boxes given below choose the one with the correct order of the following sentences. (i) That is fire. (ii) A chemical reaction takes place. (iii) Energy in the form of heat and light is released. (iv) Oxygen combines with carbon and hydrogen.– (i) (ii) (iii) (iv)– (ii) (iii) (i) (iv) – (iv) (iii) (ii) (i) – (iv) (ii) (iii) (i)

Answer» (iv) (ii) (iii) (i)
34.

What are some common uses of fire?

Answer»

Some of the common uses of fire are to cook food, warm the homes in winter and to generate electricity.

35.

What do you understand by the ‘flash point’ of a fuel?

Answer» The temperature at which a fuel begins to burn is called its flash point.
36.

(A) Roasting is a process in which the ore is heate in presence of air (R ) Concentration of sulphide ore is done by calcinaitonA. If both assertion and reason are true and reason is the correct explanation of assertion .B. if both assertion and reason are true but reason is not the correct explanation of assertionC. If assertion is true but reason is falseD. If both assertion and reason are false.

Answer» Correct Answer - D
Roasting is a process in which the ore is heated in presence of air . Sulphide ores are concentrated mainly by froth floatation process.
37.

Assertion : Magnesium metal is not used for the reduction of alumina in the metallurgy of aluminium. Reason : `MgO` curve lies above `Al_(2)O_(3)` curve in Ellingham diagram.A. If both assertion and reason are true and reason is the correct explanation of assertion .B. if both assertion and reason are true but reason is not the correct explanation of assertionC. If assertion is true but reason is falseD. If both assertion and reason are false.

Answer» Correct Answer - C
The curve for MgO lies below `Al_(2)O_(3)` in Ellingham diagram for an appreciable range of temperature and in that temperature range magnesium can reduce `Al_(2)O_(3)` , but this process is uneconomical hence, it is not used to reduce alumina.
38.

By froth flotation process, carbonate and hydroxide ores are concentrated. In froth flotation process, pine oil is used as it preferentially wets the gangue particles.A. If both (A) and ( R) are correct and ( R) is the correct explanation of (A).B. If both (A) and ( R) are correct, but ( R) is not the correct explanation of (A).C. If (A) is correct, but ( R) is incorrect.D. If (A) is incorrect, but ( R) is correct.

Answer» Correct Answer - D
Correct assertion : By froth flotation process, sulphide ores mainly are concentrated.
39.

Assertion : In electrolytic refining of metal, impure metal is made cathode while a strip of pure metal is used as anode. Reason : The pure metal gets deposited at anode as anode mud.A. If both assertion and reason are true and reason is the correct explanation of assertion .B. if both assertion and reason are true but reason is not the correct explanation of assertionC. If assertion is true but reason is falseD. If both assertion and reason are false.

Answer» Correct Answer - D
In electrolytic refining, impure metal is made anode and a strip of pure metal is made cathode. Impure metal from anode goes into solution and gets deposited as anode mud.
40.

Assertion: Nickel is purified by reaction it with `CO`. Reason: Impurities present in nickel form volatile compounds.A. If both (A) and ( R) are correct and ( R) is the correct explanation of (A).B. If both (A) and ( R) are correct, but ( R) is not the correct explanation of (A).C. If (A) is correct, but ( R) is incorrect.D. If (A) is incorrect, but ( R) is correct.

Answer» Correct Answer - C
Correct reason : `Ni` forms `Ni(CO)_(4)` on reacting with `CO`, which is a volatile compound.
41.

Assertion: Nickel is purified by reaction it with `CO`. Reason: Impurities present in nickel form volatile compounds.A. If both assertion and reason are true and reason is the correct explanation of assertion .B. if both assertion and reason are true but reason is not the correct explanation of assertionC. If assertion is true but reason is falseD. If both assertion and reason are false.

Answer» Correct Answer - C
Ni reacts with CO to form nickel tetracarbonyl.
42.

Assertion: Nickel is purified by reaction it with `CO`. Reason: Impurities present in nickel form volatile compounds.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is false.D. If assertion is false but reason is true.

Answer» Correct Answer - C
Correct Reason: Nickel reacts with `CO` to from volatile `Ni(CO)_(4)`.
43.

Assertion : Aluminium is used for the extraction of chromium from its oxide Reason : Aluminium has high melting point.A. Both assertion and reason are correct statements, and reason is the correct explanation of the assertion.B. Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion.C. Assertion is correct, but reason is wrong statement.D. Assertion is wrong, but reason is correct statement.

Answer» Correct Answer - B
Correct explanation : Aluminium is a stronger reducing agent than chromium.
44.

Assertion: Aluminothermy is used for extraction of chromium form chromium oxide. Reason: Alumina has a high melting point.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertion.C. If assertion is true but reason is false.D. If assertion is false but reason is true.

Answer» Correct Answer - B
Correct Reason: `Delta_(f)G^(@)` for formation of `A1_(2)O_(3)` is much more-ve than that of `Cr_(2)O_(3)`.
45.

Why do colloidal particles show Brownian movement ?

Answer»

(Hint : Due to unbalanced bombardment of the dispersed phase particles by the molecules of the dispersion medium.)

46.

Why do transition metals show variable oxidation state?

Answer»

Due to nearly same energy of 45 & 3d orbitals of tr. metal, electrons of there orbitals participate in bond formation. Hence oxidation states of tr. metals is variable.

47.

Write about Half-time of a reaction

Answer»

Half time of a reaction:-

The time taken for a reaction when half of the reactant has reactaed is called Half time of reaction and donoted by t1/2.

48.

Write about Brownian movement

Answer»

Brownian movement:-

It involves the motion of colloidal particles in Zig-Zag Paths.

49.

Write IUPAC name of K4[Fe(CN)6]

Answer»

Potassium hexa cyno ferrate (II)

50.

Define point defect. Why is Frenkel defect produced in solid crystal?

Answer»

Point defect:-

The defect in which irregularties from ideal arrangement around a point occur, is called point defect.

The defect arrise when some of the ions of the lattice occupy interstitial sites leaving lattice site vacent is called frenkel defect. This defect occurs in ionic crystal where anion is much larger in size then the cation.

ex. AgBr, ZnS.