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(i) A yellow precipitate of lead iodide (PbI₂) is formed.
(ii) Precipitation reaction/Double displacement reaction.
(iii) Pb(NO₃)₂(aq) + 2KI(aq) ------> PbI₂(s) +   2KNO₃ (aq)
Lead nitrate           Potassium iodide    Lead iodide     Potassium nitrate

                                                              (Yellow ppt.)     

Yes, the reproductive health has tremendously improved in India in the last 50 years. The areas of improvement are as follows.

• Massive child immunization programme, which has lead to a decrease in the infant mortality rate
• Maternal and infant mortality rate, which has been decreased drastically due to better postnatal care
•  Family planning, which has motivated people to have smaller families
•  Use of contraceptive, which has resulted in a decrease in the rate of sexually transmitted diseases and unwanted pregnancies

In aqueous solutions, strong acids ionise completely and provide hydronium ions. On the other hand, weak acids are partially ionised and an aqueous solution of same molar concentration provides a much smaller concentration of H₃O⁺ ions. 

Strong acids Hydrochloric acid, sulphuric acid, nitric acid. 

Weak acids-Citric acid, acetic acid, formic acid.

The resultant of two vectors P and Q is given by:- 

\(R^2 = P^2 + Q^2 + 2PQ\cos \theta\) 

By Using this formula, we get, 

R² = 6² + 8² + 2(6)(8) cos240°

R² = 36 + 64 + (2 × 48 × -1/2)

R² = 100 - 48 = 52

R = 2√13

Hence, the magnitude of resultant of forces is 2√13 N. 

Molecular mass of FeSO₄. 7H₂O is

→ 55 + 32 + 16×4 + 7(1×2+16)

→ 55 + 32 + 64 + 7(18)

→ 55 + 32 + 64 + 126

→ 277 g/mol

Hence,

The molar mass of FeSO₄.7H₂O is 277 g/mol.

(c) fibrocartilage

FRANCE currently has the third largest number of satellites in orbit.

RADON occurring radioactive substance present in indoor air is suspected as the second leading cause of lung cancer.

INDIA was a method for making rust-resistant iron discovered in the fifth century B.C.

1. Adipose tissue – beneath the skin 

2. Ligament – attach one bone to another 

3. Cardiac muscle – heart

 BARK AND LEAVES OF THE YEW TREE 

(a) Juvenile phase:
It is the period of growth in an individual organism after its birth and before it reaches reproductive maturity.
(b) Reproductive phase:
It is the period when an individual organism reproduces sexually.
(c) Senescent phase:
It is the period when an organism grows old and loses the ability to reproduce.

(i) Definition: “when a constraint applied to a system at equilibrium in a reversible reaction, the equilibrium shifts so as to nullify the constraint”. 

[Constraint is change in temperature or pressure, addition of reactant or product] 

(ii) Supression in degree of dissociation of a weak electrolyte by addition of a common ion is called common ion effect. 

Example: CH₃COOH and CH₃COONa

(d) 1, 3 and 4 are correct

The correct answer is Naga Hills.

• The ongoing national movement influenced the tribal movements in the early decades of 20th century: The Tana Bhagat movement of Gumla in Ranchi district, and the Zeliangrong movement in the Naga Hills were two such instances.
• Jadonang (1905-1931), who set up the Haraka religious cult with three basic objectives started the complex Zeliangrong or Haomei movement in 1925.
  • The first aimed at reformation of the tribes, particularly the Zemi, Liangrnei and Rangmei, to enable them to face the onslaught of Christianity.
  • Secondly, the overthrows of the exploitative colonial laws by attacking British rule.
  • And third, establishment of the Naga Raj.
• The movement was also aimed against the Kuki tribe, the “outsider”.
• From 1927 onwards, influenced by Gandhi, Jadonang began a civil disobedience movement in the area.
• On 13 June 1931, Jgdonang was arrested and sentenced to death, and finally hanged on 29 August 1931.

(-R₂SiO^-) is the repeating unit.

Methyl chloride and silicon in presence of copper as catalyst at temperature 573K are the starting material.

R₂SiO. The starting material is alyl or aryl-substituted silicon chlorides.

Answer is 3s < 3p

1s² 2s² 2p⁶ 3s² 3p⁶4s²

Answer is 1s< 2s

Answer is [Ne] 3s¹

v̄ = 1.09 × 10⁷ m^-1 (1/2² - 1/0)

v̄ = 1.09 × 10⁷ (1/4) 

v̄ = 0.2725 × 10⁷ 

v̄ = 2.725 × 10⁶ m^-1

It is impossible to determine both the momentum (particle nature) and position (wave nature) of a moving subatomic particle simultaneously with absolute accuracy. 

Mathematically Δx × Δp = h / 4π where Δx = uncertainty in position: 

Δp = uncertainty in momentum ; h = Plank’s constant = 6.626 × 10^-34 Js.

Answer is 2, 8, 8, 1

Group Number — 1

Period number — 3

a. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²

b. Group number – 8, Block – d 

c. All of them are metals d – block elements are placed in group 3 to group 12 

d. s – Sub shell

Fluorine F, Period – 2, p block, Group 17

Atomic Number

a. G 

b.F 

c. The element having highest atomic radius – A The element having lowest Atomic radius – H 

d. D, C 

e. H

• The outermost p subshell of the p block elements contains 1 to 6 electrons. 
• Elements showing positive oxidation state and negative oxidation state are members of this block. 
• There are metals and nonmetals in these blocks. 
• Elements in the solid, liquid and gaseous states are present in p block.

Group 18 elements.

a.

b. X Y

c.

a.  X₂₈ – 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 4s² 

X²⁺ – 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁸ 

b. d block Compound 

c. 1. It exhibits variable oxidation states 

2. Forms colored compounds 

3. Last electron enters d subshell

a. Halogen

b. 1

c. F

d. F

e. 

• sodium chloride – NaCl 
• potassium chloride – KCl 
• magnesium chloride- MgCl₂
• calcium chloride- CaCl₂
• magnesium fluoride- MgF₂ 
• calcium fluoride – Ca F₂ 
• sodium iodide – Nal 
• potassium iodide – KI 
• potassium bromide – KBr 
• potassium fluoride – KF

s-block elements: 

Elements in which last electron enters into s-subshell are called s-block elements. It contains group I elements (Alkali metals) and group II elements (Alkaline earth metals)

1st group elements lose one electron during chemical combination. Therefore its oxidation state is +1. 

2nd group elements lose two electrons from valence shell during chemical combination and their oxidation state is +2. 

The highest shell number in a sub-shell electronic configuration is the period number of that element.

1. Group number characteristics = no.of electrons in valence sub-shell. 

2. s block ionization energy & electro negativity decreases downwards. 

3. Metallic character & reactivity increases downwards. 

4. Lose electrons during chemical combination j and they form ionic compounds. Their oxides and hydroxides are basic. Their atomic radii are high in a period.

p-block elements: 

• Last electron enters into p-subshell. 
• Group 13 -18 elements. 
• Highly reactive elements are nonmetals – group 17, 
• These are elements with positive and negative oxidation state.

Group number of p-block elements = electrons in last p-subshell + 12 

d-block elements: 

• Last electron enters into penultimate d-subshell 
• Known as transition elements. 
• Metals 
• Shows similarity in group and period. 
• Variable oxidation states. 
• Form coloured compounds.

Group = electrons in ‘d’-subshdl + electrons in s-subshell. 

f-block elements:

• Last electron enters into antepenultimate f sub-shell. 
• Contains Lanthanoids and Actinoids. 
• Variable oxidation state. 
• Most of the Actinoids are radioactive. 
• Most of the elements are artificial. 
• U, Th, Pu are used in nuclear reactors. 
• Some elements are used as catalyst in pet-roleum industry.

Answer is 6 Electrons