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JEE Chemistry Solved Question Paper 2015

Multiple Choice Questions

31.

How many ions per molecule are produced in the solution, when Mohr salt is dissolved in excess of water?

32.

Which of the following aqueous solution has the highest freezing point?

0.1M surcose
0.01 M NaCl
0.1 M NaCl
0.01 M Na₂SO₄

33.
Half-life period of a first order reaction is 10 min. Starting with initial concentration 12 M, the rate after 20 min is

0.0693 M min^-1

0.693 × 3M min^-1

0.0693 × 3M min^-1

0.0493 × 4M min^-1

0.0693 × 3M min^-1

Rate constant remains same throughout the reaction. For first order reaction, half-life of the reactant does not depend upon the its concentration. Hence, we can easily calculate the value of rate constant with the help of provided half-hie value by using the formula t_1/2= 0.693/k. Now, we can calculate the k concentration of reactant after 20min and then rate of reaction.

Given, t_1/2 = 10min

$since, t_{1 / 2} = \frac{0.693}{k} (k = rate constant) k = \frac{0.693}{10} = 0.0693$

Stage	Time	Concentration
Intial	t=0	12M
	t_1/2 =10 min	6M
	t = 20min	3M

Since, it is a first order reaction.

Rate = k[A] = 0.069 × 3M min^-1

34.

The salt which responds to dilute and concentrated H₂SO₄ is

CaF₂
Ba(NO₃)₂
Na₂SO₄
Na₃PO₄

35.

The aqueous solution of following salt will have the lowest pH

NaClO₃
NaClO
NaClO₂
NaClO₄

36.

For one of the element various successive ionisation enthalpies (in kJ mol^-1) are given below.

	1st	2nd	3rd	4th	5th
IE	5775	1810	2750	11,580	14820

The element is

37.

How many Coulombs of electricity are required for the oxidation of one mole of water to dioxygen?

9.65 × 10⁴ C
1.93 × 10⁴ C
1.93 × 10⁵ C
19.3 × 10⁵ C

38.

Which of the following colloids cannot be easily coagulated?

Lyophobic colloids
Multimolecular colloids
Macromolecular colloids
Irreversible colloids

39.

The complex ion having minimum magnitude of Δ_° (CFSE) is

[Cr(CN)₆]^3-
[Co(CN₃)₆]³⁺
[Co(Cl)₆]³⁺
[Cr(H₂O)₆]³⁺

40.

Cryolite is

Na₃AlF₆ and is used in the electrolysis of alumina for decreasing electrical conductivity
Na₃AlF₆and is used in the electrolysis of alumina for lowering the melting point of alumina only ·
Na₃AlF₆and is used in the electrolysis of alumina for lowering the melting point and increasing the conductivity of alumina
Na₃AlF₆and is used in the electrolytic refining of alumina