Question

2. The rate of reaction for R → products over the time period 15 to 30 s is 0.0036 M/s. If the concentration of a reactant at 15 s is 0.39M, what is the concentration at 30 s?

1. From the data below, calculate the rate of reaction over the time period 10 to 25 s.

time (s)	concentration (M)
0	1.00
5	0.61
10	0.37
15	0.22
20	0.14
25	0.082
30	0.050

Answer 1

2.

Rate (r) = change in concentration / time interval

Given that

Concentration at 15 s= 0.39 M

Concentration at 30 s= ? M

  Rate = 0.0036 M/s

Time period 15 to 30S

Then;

Rate (r) = change in concentration / time interval

0.0036M/s = Concentration at 30 s - Concentration at 15 s/ 30s-15s

0.0036M/s = Concentration at 30 s – 0.39 M / 30s-15s

Concentration at 30 s= 0.054 M + 0.39 M

= 0.444 M

1.

To calculate the rate of reaction over the time period 10 to 25 s use following expression:

Rate (r) = change in concentration / time interval

Given that

Concentration at 10 s= 0.37 M

Concentration at 25 s= 0.082 M

  Rate = ? M/s

Time period 10 to25 S

Then;

Rate (r) = change in concentration / time interval

= 0.082- 0.37 / 25-10 Ms-1

= -0.0192 M/s

Negative sign indicates decreasing in concentration