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1. Example Question 18.01 [18.02 Rate Laws | Integrated Rate Laws ] [Answer: (a)

ID: 908431 • Letter: 1

Question

1. Example Question 18.01 [18.02 Rate Laws | Integrated Rate Laws ] [Answer: (a) t1/2 = |247 min; (b) t = 819 min; (c) 10.9 g.] Sulfuryl chloride, SO2Cl2, decomposes by first-order kinetics, and k = 2.81 x 10^-3 min^-1 at a certain temperature. (a) Determine the half-life for the reaction. (b) Determine the time needed for the concentration of SO2Cl2 to decrease to 10 % of its initial concentration. (c) 14.0 g of SO2Cl2 is sealed in a 2500.-L reaction vessel and heated to the specified temperature, what mass will remain after 1.5 h?

Explanation / Answer

(a) For a first order reaction,

t1/2 = 0.693/k = 0.693/2.81 x 10^-3 = 247 min

(b) For a first order reaction,

ln([A]/[Ao]) = - kt

Where,

[A] = substrate concentration remaining after t time

[Ao] = initial substrate concentration

[A]/[Ao] = 1/10

k = 2.81 x 10^-3 min-1

Feed values,

ln(1/10) = -2.81 x 10^-3 x t

So the time needed to reduce the concentration to 10%,

t = 819.42 min

(c) [Ao] = 14.0 g

t = 1.5 h = 1.5 x 60 = 90 min

Feed values,

ln[A] = ln[Ao] - kt

        = ln(14) - 2.81 x 10^-3 x 90

Mass remaining after 1.5 h would be,

[A] = 10.90 g