CHEMICAL KINETICS QUIZ-4

Q1. Give relation between half reaction time (t_(1/2))and initial concentration of reactant for (n-1)order reaction.

•  t_(1/2)∝[R]_0
•  t_(1/2)∝[R]_0^(n-2)
•  t_(1/2)∝[R]_0^(n+1)
•  t_(1/2)∝[R]_0^(2-n)

Solution
Relation between (t_(1/2))and initial concentration of reactant for (n-1)order reaction t_(1/2)∝[R]_0^(2-n)

Q2.For the reaction N_2+3H_2⇌2NH_3 The rate of change of concentration for hydrogen is 0.3×〖10〗^(-4) Ms^(-1) The rates of change of concentration of ammonia is

•  -0.2×〖10〗^(-4)
•  0.2×〖10〗^(-4)
•  0.1×〖10〗^(-4)
•  0.3×〖10〗^(-4)

Solution

Q3.  For the reaction system 2NO(g)+O_2 (g)→2NO_2 (g) if the volume of the reaction vessel is reduced to one-third of its original volume, what will be the order of the reaction?

•   Diminished to one fourth of its initial value
•  Diminished to one twenty seven of its initial value
•  Increase to four times of its initial value
•  Increase to twenty seven times of its initial value

Solution

Q4. The rate constant of nth order has units:

•  litre^(1-n) mol^(1-n) sec^(-1)⁡
•  mol^(n-1) litre^(n-1) sec^(-1)⁡
•  None of these
•  mol^(1-n) litre^(n-1) sec^(-1)⁡

Solution
For nth order; unit of rate constant may be derived by K=rate/[reactant]^n

Q5.In the reaction; A+2B⟶3C+D which of the following expressions does not describe changes in the concentration of various species as a function of time?

•  (2d[B])/dt=(d[A])/dt
•  (3d[B])/dt=(-2d[C])/dt
•  (3d[D])/dt=(d[C])/dt
•  (d[C])/dt=(-3d[A])/dt

Solution
 For the given reaction, (-d[A])/dt=-1/2 d[B]/dt=1/3 d[C]/dt=(d[D])/dt

Q6. The velocity constant of a reaction at 290 K was found to be 3.2×〖10〗^(-3) s^(-1). When the temperature is raised to 310 K, it will be about

•  6.4×〖10〗^(-3)
•  1.28×〖10〗^(-2)
• 9.6×〖10〗^(-3)
•  3.2×〖10〗^(-4)

Solution
Rate constant almost gets doubled by the increase of 10℃ in temperature. Hence, the rate constant at 310 K will be =3.2×〖10〗^(-3)×(2)^2 ( ∵increase in temperature=20 K) =1.28×〖10〗^(-2) J^(-1)

Q7.The term (-dc)/dt in a rate equation refers to

•  The velocity constant of the reaction
•  The change in concentration of the reactant
•  TThe decrease in concentration of the reactant with time
•  The concentration of the reactant

Solution
dc/dt represent the change in concentration of reactant with time. As, in a reaction, concentration of reactant always decrease with time hence, rate of reaction is represented as (-dc)/dt.

Q8.The following data were obtained the first order decomposition of 2 A(g)→B(g)+C(S) at a constant volume and at a particular temperature SN Time Total pressure in Pascal 1 At the end of 10 min 300 2 After completion 200 The rate constant in min┴(-1)⁡〖is 〗

•  69.3
•  0.0693
•  6.93
•  6.93×〖10〗^(-4)

Solution

Q9.For a chemical reaction 2X+Y→Z, the rate of appearance of Z is 0.05 mol L^(-1). The rate of disappearance of X will be

•  0.05 mol L^(-1) h^(-1)
•  0.05 mol L^(-1) min^(-1)
•  0.25 mol L^(-1) min^(-1)
•  0.1 mol L^(-1) min^(-1)

Solution

Q10. An endothermic reaction A→B has an activation energy as x kg mol^(-1) of A. If energy change of the reaction is y kJ, the activation energy of the reverse reactions is

•  x+y
•  x-y
•  y-x
• -x

Solution