In a first order reaction, the concentration of the reactant is decreased from 1.0 M to 0.25M in 20 minute. The rate constant of the reaction would be:

(1) 10min^-1

(2) 6.931 min^-1

(3) 0.6931 min^-1

(4) 0.06931 min^-1

The rate constant of a first order reaction is 4x10^-3 sec^-1. At a reactant concentration of 0.02 M, the rate of reaction would be:

(a) 8 x 10^-5 Msec^-1

(b) 4 x 10^-3 Msec^-1

(c) 2 x 10^-1 Msec^-1

(d) 4 x 10^-1 Msec^-1

If concentration of reactants is increased by 'X', the rate constant K becomes:

(a) e^K/X

(b) K/X

(c) K

(d) X/K

A graph plotted between log (t) 50% vs. log (a) concentration is a straight line. What conclusion can you draw from the given graph?

(a) n=1, t_1/2 = 1/K.a

(b) n=2, t_1/2 = 1/a

(c) n=1, t_1/2 = 0.693/K

(d) None of the above

The rate of a chemical reaction doubles for every 10°C rise of temperature. If the temperature is raised by 50°C, the rate of the reaction increases by about :

(a) 10 times

(b) 24 times

(c) 32 times

(d) 64 times

Consider the reaction:

Cl₂(aq) + H₂S(aq) → S(s) +2H⁺(aq) +2Cl^-(aq)

The rate equation for this reaction is rate = k[Cl₂][H₂S] Which of these mechanisms is/are consistent with this rate equation?

A. Cl₂ + H₂S → H⁺ + Cl^- +Cl⁺ + HS^- (slow)

cl⁺ + HS^- → H⁺ +Cl^- + S (fast)

B. H₂S $\iff$ H⁺ + HS^- (fast equilibrium)

Cl₂ + HS^- → 2Cl^- + H⁺ + S (slow)

(1) A only

(2) B only

(3) Both A and B

(4) Neither A nor B

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

1. Exothermic

2. Endothermic

3. Neither exothermic nor endothermic

4. Independent of temperature

The t_0.5 for the first order reaction.

PCl₅(g) $\to$PCl₃(g) + Cl₂(g) is 20 min. The time in which the conc. of PCl₅ reduces to 25% of the initial conc. is close to 

1. 22 min

2. 40 min

3. 90 min

4. 50 min

For a certain reaction, 10% of the reactant dissociates in 1 hour, 20% of the reactant dissociate in 2 hour, 30% of the reactant dissociates in 3 hour. Then the units of the rate constant is:-

(1) hour^-1

(2) mol L^-1 hr^-1

(3) L mol L^-1 sec^-1

(4) mol L sec^-1

The activation energy of a reaction is zero. The rate constant of the reaction is :

(1) Increases with increase in temperature

(2) Decreases with decrease in temperature

(3) Decreases with increase in temperature

(4) Is nearly independent of temperature