A first-order reaction has a specific reaction rate of 10^–2 s^–1. How much time will it take for 20 g of the reactant to reduce to 5 g?

• 238.6 second

• 138.6 second

• 346.5 second

• 693.0 second

B.

138.6 second

For the reduction of 20 g of reactant to 5 g, two t_1/2 is required.

Activation energy (E_a) and rate constants (k₁ and k₂) of chemical reaction at two different temperatures (T₁ and T₂) are related by

• 
• 
• 
• 

D.

According to Arrhenius equation, activation energy (E_a) and rate constants (k₁ and k₂) of chemical reaction at two different temperatures (T₁ and T₂) are related as,

Consider the reaction

N₂ (g) + 3 H₂ (g) → 2 NH₃ (g) 

The equality relationship between   is:

• 
• 
• 
• 

B.

For the reaction,
N₂ (g) + 3 H₂ (g) → 2 NH₃ (g)

During the kinetic study of the reaction, 2A + B --> C+ D,  following results were obtained 

	[A]/mol L-	[B]/ mol L-	Initial rate of formation of D/ mol L- min-
I	0.1	0.1	6.0 x 10-3
II	0.3	0.2	7.2 x 10-2
III	0.3	0.4	2.88 x 10-1
IV	0.4	0.1	2.40 x10-2

 
based on the above data which one of the following is correct?

• rate = k[A]²[B]

• rate = k [A][B]

• rate = k[A]²[B]²

• rate = k[A][B]²

D.

rate = k[A][B]²

Let the order of reaction with respect to A is x and with respect to B is y. Thus,
rate = k[A]^x[B]^y
For the given cases,

(I) rate = k(0.1)^x (0.1)^y = 6.0 x 10^-3
(II) rate = k (0.3)^x (0.2)^y = 7.2 x 10^-2
(III) rate =k(0.3)^x (0.40)^y = 2.88 x 10^-1
(IV) rate = k(0.4)^x (0.1)^y = 2.40 x 10^-2

On dividing eq. (I) and (IV), we get

For an endothermic reaction, energy of activation is E_a and enthalpy of reaction is ΔH (both of these in kJ/mol). Minimum value of E_a will be

• less than ΔH

• equal to ΔH

• more than ΔH

• equal to zero