Rate laws 1. Sulfuryl chloride (SO 2 Cl 2 ) decomposes on heating: SO 2 Cl 2(g)

Question

Rate laws

1. Sulfuryl chloride (SO2Cl2) decomposes on heating:

SO2Cl2(g) --> SO2(g) + Cl2(g)

The kinetics of this reaction are described by the equation d[SO2]/dt = k[SO2Cl2]. Write down the part or parts of this equation which correspond to the following terms:

(a) the rate of the reaction

(b) the rate constant for the reaction

(c) the rate law (also called the rate expression)

2. Which of (a), (b) and (c) change during the reaction?

3. The decomposition of H2O2 is studied by determining the concentration of hydrogen peroxide at various times during the reaction by titration with potassium permanganate in acidic solution. The decomposition is first-order. In one experiment it was found that the half-life (t1/2) for the decomposition was 10.0 minutes. Complete the following table by predicting the volumes of the KMnO4 solution required to react with the H2O2 after it has been decomposing for 15.0 minutes and 25.0 minutes.

5min = 30.40mL

15min = ___mL

25min = ___mL

(a) Calculate the rate constant for the decomposition described above.

Give the units of the rate constant.

(b) Using the value of the rate constant calculated in (a), determine the concentration of H2O2 that has reacted after it has been decomposing for 8.0 minutes. The initial concentration of the H2O2 was 0.0800M.

Explanation / Answer

1)

rate of reaction and rate law will vary   answer is a and c

2)

after 5minute = 30ml

K = 1/T * (log(initial conc/final concentration))

t1/2 = 10 minute = 0.693/k

so rate constant K = 0.0693 minute-1

After 5 minute = 0.0693 = (1/5) * (log(initial/30.40)))

Initial concentration 42.98ml of 0.08M H2O2

After 15 minute = 0.0693 = (1/15) * (log(42.98/x)))

               = 15.17ml of 0.08M H2O2

After 25 minute = 0.0693 = (1/25) * (log(42.9/x))

                =7.58mlof 0.08M H2O2

After 8 minute 0.0693 = (1/8) * (log(42.9/x))

                 = 24.64 ml of 0.08M H2O2 will be left over

So reacted H2O2 after 8 minute = 42.98-24.64 = 18.34 ml of 0.08M H2O2 has reacted

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