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1. At 25°C the rate constant for the first-order decomposition of a pesticide so

ID: 497067 • Letter: 1

Question

1. At 25°C the rate constant for the first-order decomposition of a pesticide solution is 1.50 * 10–3 min–1.  If the starting concentration of pesticide is 0.750 M, what concentration will remain after 62.0 min at 25°C?

2.

Nitric oxide gas (NO) reacts with chlorine gas according to the chemical equation given below.

            NO + Cl2 NOCl

            The following initial rates of reaction have been measured for the given reagent concentrations. Determine the rate law of this reation?

Expt. #

Rate (M/hr)

NO (M)

Cl2 (M)

1

1.19

0.50

0.50

2

4.79

1.00

0.50

3

9.59

1.00

1.00

Expt. #

Rate (M/hr)

NO (M)

Cl2 (M)

1

1.19

0.50

0.50

2

4.79

1.00

0.50

3

9.59

1.00

1.00

Explanation / Answer

1)
use integrated rate law for 1st order reaction:
ln [A] = –kt + ln [A]o
ln [A] = -(1.50*10^-3 * 62.0) + ln (0.750)
ln [A] = -0.381
[A] = 0.683 M

Answer: 0.683 M

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