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

If the activation energy of a reaction is zero, how does the rate constant of the reaction change with temperature?

1. Increases with the increase in temperature

2. Decreases with the decrease in temperature

3. Decreases with the increase in temperature

4. Is nearly independent of temperature