Question

A first-order reaction has a rate constant of 0.241/min. if the initial concentration of a is 0.859 m, what is the concentration of a after 10.0 minutes?

Answer 1

Answer: 0.077 M

Explanation:

Expression for rate law for first order kinetics is given by:

$k=\frac{2.303}{t}\log\frac{a}{a-x}$

where,

k = rate constant = $0.241minute^{-1}$

t = time taken for decay process = 10 minutes

a = initial amount of the reactant= 0.859 M

a - x = amount left after decay process =?

Putting values in above equation, we get:

$0.241 minutes^{-1}=\frac{2.303}{10.0}\log\frac{0.859}{a-x}$

$(a-x)=0.077M$

Thus the concentration of a after 10.0 minutes is 0.077 M.

Answer 2

Initial concentration is 0.859 m.
A rate: 0.241 m/min.
In 10 minutes: 10 min * 0.241 m/min = 2.41 m
0.859 m + 2.41 = 3.269 m
Answer: After 10 minutes the concentration is 3.269 m.