In a reaction, a chemist is observing the absorbance of CoCl2(aq) as a function of time to determine the rate at which it is being consumed in a reaction. At time t=10 s, the chemist determines that the concentration of CoCl2(aq) is 0.12 M. At time t=20 s, the chemist determines that the concentration of the CoCl2(aq) is 0.090 M. What is the average rate of the consumption of CoCl2 over this time period?

Question

In a reaction, a chemist is observing the absorbance of CoCl2(aq) as a function of time to determine the rate at which it is being consumed in a reaction. At time t=10 s, the chemist determines that the concentration of CoCl2(aq) is 0.12 M. At time t=20 s, the chemist determines that the concentration of the CoCl2(aq) is 0.090 M. What is the average rate of the consumption of CoCl2 over this time period?

a.
0.30 M/s

b.
2.1 M/s

c.
300 M/s

d.
0.003 M/s

e.
0.021 M/s

Answer 1

delta C = 0.12-0.09 = ?

time = 20s - 10s = ?
Avg = delta C/delta t = ?

Answer 2

To determine the average rate of the consumption of CoCl2 over the given time period, we need to use the formula for average rate:

Average rate = (Change in concentration)/(Change in time)

First, we calculate the change in concentration:

Change in concentration = final concentration - initial concentration
= 0.090 M - 0.12 M
= -0.030 M (negative because the concentration is decreasing)

Next, we calculate the change in time:

Change in time = final time - initial time
= 20 s - 10 s
= 10 s

Now, we can calculate the average rate:

Average rate = (Change in concentration)/(Change in time)
= (-0.030 M)/(10 s)
= -0.003 M/s

The answer is -0.003 M/s. However, since the question is asking for the average rate of consumption, we can drop the negative sign and the answer becomes 0.003 M/s.

Therefore, the correct answer is (d) 0.003 M/s.