Chemical Kinetics Test

Result

Chemical Kinetics Test - 9

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Weekly Quiz Competition

Question 1
1 / -0

The rate constant of a reaction is 1.5 × 10⁷ sec^-1 at 50 ° C and 4.5 × 10⁷ sec^-1 at 100 ° C. The Arrhenius parameters Ea and A are?

A
3.3 × 10⁴ J mol^-1 & 8.42 × 10¹⁰

B
4.2 × 10⁴ J mol^-1 & 8.42 ×10¹⁰

C
2.2 × 10⁴ J mol^-1 & 5.42 × 10¹⁰

D
None of these

Solution

2.303 log₁₀ (K₂/K₁) = (Ea/R)[(T₂ – T₁)/T₁T₂]

Therefore, 2.303 log₁₀{(4.5 × 10⁷)/(1.5 × 10⁷)} = (Ea/8.314)[(373 – 323)/373 × 323]

Therefore, Ea = 2.2 × 10⁴ J mol^-1

Now, K = Ae^–Ea/RT

Therefore, 4.5 × 107 = Ae^{–{(2.2 × 104)/(8.314 × 373)}}

Therefore, A = 5.42 × 10¹⁰
Question 2
1 / -0

The activation energies of the forward and backward reactions in the case of a chemical reaction are 30.5 and 45.4 KJ/mol respectively. The reaction is?

A
Exothermic

B
Endothermic

C
Neither exothermic nor endothermic

D
Independent of temperature

Solution

Enthalpy of reaction = activation forward – activation backward

Enthalpy = 30.5 – 45.4 < 0

Hence, it is exothermic reaction.
Question 3
1 / -0

for a chemical reaction 3A + B⟶ product

It was observed that rate of reaction increases nine times when concentration of B increased three times by keeping concentration of A as constant. On doubling concentration of both rate increases eight times. Differential rate equation can be given as

A
r = k [A] [B]³

B
r = k [A] [B]²

C
r = k [A]² [B]

D
r = k [A]² [B]^1/3

Solution

r = k [A] [B]²

Assume that

now, r = k [A]ⁿ [B]^m

rate of reaction increases 9 times when concentration of B increases 3 times by keeping concentration of A as constant.

9r = K [A]ⁿ [3B]^m

9r = K [A]ⁿ 3^m [B]^m

9r = 3^m r

9 = 3^m

m = 2

On doubling the concentration of both, rate increases eight times,

8r = K [2A]ⁿ [2B]²

8r = K 2ⁿ [A]ⁿ 2² [B]²

8r = K 2ⁿ 2² [A]ⁿ [B]²

8r = 2ⁿ 2²r

8 = 2ⁿ 4

n = 1
hence, r = k [A] [B]²
Question 4
1 / -0

Which of them is not true according to collision theory of reaction rates ?

A
Collision of molecules is a precondition for any reaction to occur

B
All collision result in the formation of products

C
Only activated collision result in formation of products

D
Molecules which have acquired the energy of activation can collide effectively

Solution

All collisions are not effective and does not result in the formation of products.