Question

10 and 11

10. Nitrosyl chloride, NOCI, decomposes slowly to NO and Cl2, the reaction follows second order kinetics with a rate constant of 0.020 L mol-' s at a certain temperature. 2 NOCI (g) → 2 NO(g) + Cl2(g) If the initial concentration of NOCI in a closed reaction vessel is 0.050 M, what will be the concentration be after 30 minutes? 11. The reaction 2 NO2 (g) → 2 NO(g) + O2(g), is second order with respect to NO2. If the initial concentration of NO2 is 6.54 x 10-4 mol/L, what is the rate constant if the initial reaction rate is 4.42 x 10-7 M/s? What is the half-life of this reaction? n

Answer 1

10)

we have:

[NOCl]o = 0.050 M

t = 1800.0 s

k = 2*10^-2 M-1.s-1

use integrated rate law for 2nd order reaction

1/[NOCl] = 1/[NOCl]o + k*t

1/[NOCl] = 1/(5.00*10^-2) + 2*10^-2*1.8*10^3

1/[NOCl] = 20 + 2*10^-2*1.8*10^3

1/[NOCl] = 56

[NOCl] = 1.786*10^-2 M

Answer: 1.79*10^-2 M

11)

Rate = k [NO2]^2

Put values

4.42*10^-7 M/s = k (6.54*10^-4 M)^2

K = 1.04 M-1.s-1

Answer: 1.04 M-1.s-1