Chemistry Test 179

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Chemistry Test 179

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Weekly Quiz Competition

Question 1
4 / -1

Consider the following reaction:

N₂O₄(g) ⇋ 2NO₂(g); ΔH⁰ = +58 kJ

For each of the following cases (a, b), the direction in which the equilibrium shifts is:

(a) Temperature is decreased.

(b) Pressure is increased by adding N₂ at constant T.

A
(a) Towards product, (b) towards reactant

B
(a) Towards reactant, (b) no change

C
(a) Towards reactant, (b) towards product

D
(a) Towards product, (b) no change

Solution

(a) temp↓ ⇒ Backward shift as it is an endothermic reaction

(b) As 'N₂' will not react with both N₂O₄ and NO₂, there will be no change in equilibria.
Question 2
4 / -1

For the reaction

Fe₂N(s) + 3/2 H₂(g) ⇋ 2Fe(s) + NH₃(g),

A
K_C = K_p (RT)^1/2

B
K_C = K_p (RT)

C
K_C = K_p (RT)^3/2

D
K_C = K_p (RT)^-1/2

Solution

K_p = K_c(RT)^Δ^ng as Δn_g = 1 – 3/2 = –1/2

K_p = K_c(RT)^–1/2

K_c = K_p(RT)^1/2
Question 3
4 / -1

A
1.8 × 10^-9

B
1.8 × 10⁹

C
5.55 × 10^-9

D
5.55 × 10¹⁰

Solution
Question 4
4 / -1

The first and second dissociation constants of an acid H₂A are 1.0 × 10^-5 and 5.0 × 10^-10 respectively.

The overall dissociation constant of the acid will be:

A
5.0×10^-5

B
5.0×10¹⁵

C
5.0×10^-15

D
0.2×10⁵

Solution
Question 5
4 / -1

What volume of 0.2 M NH₄Cl solution should be added to 100 ml of 0.1 M NH₄OH solution to produce a buffer solution of pH = 8.7 ?

Given : pK_b of NH₄OH = 4.7 ; log 2 = 0.3

A
50 ml

B
100 ml

C
200 ml

D
none of these

Solution
Question 6
4 / -1

How many gm of solid NaOH must be added to 100 ml of a buffer solution which is 0.1 M each w.r.t. Acid HA and salt Na⁺ A^- to make the pH of solution 5.5. Given pK_a(HA) = 5 (Use antilog (0.5)= 3.16)

A
2.08 × 10^-1

B
3.05 × 10^-3

C
2.01 × 10^-2

D
None of these

Solution
Question 7
4 / -1

100 mL of 0.1 M HCl is taken in a beaker and to it 100 mL of 0.1 M NaOH is added in steps of 2 mL and the pH is continuously measured.

Which of the following graphs correctly depicts the change in pH?

A

B

C

D

Solution

For titration between HCl and NaOH, pH at equivalence point is found to be 7 and the graph should depict a sharp increase in the pH value at the equivalence point.

Hence, option (1) is correct.
Question 8
4 / -1

How many litres of water must be added to 1 litre of an aqueous solution of HCl with pH = 1 to create an aqueous solution with pH = 2?

A
0.9 L

B
2.0 L

C
9.0 L

D
0.1 L

Solution

Initial pH = 1, i.e. [H⁺] = 0.1 mole/litre

New pH = 2, i.e. [H⁺] = 0.01 mole/litre

In case of dilution: M₁V₁ = M₂V₂

0.1 × 1 = 0.01 × V₂

V₂ = 10 litres

Volume of water added = 9 litres
Question 9
4 / -1

Which one of the following solutions has the maximum pH value?

A
0.2 M HNO₃

B
0.2 M HCI

C
0.2 M HC₂H₃O₂

D
0.2 M NaC₂H₃O₂

Solution

Sodium acetate solution (0.2 M NaC₂H₃O₂solution) will be alkaline and thus, will have the maximum pH value.
Question 10
4 / -1

The pH of 0.1 M NH₄OH (K_b = 1.8 × 10^–5 M) at 25°C is

A
12.87

B
13.8

C
11.13

D
12.2

Solution