Question

The rate constant for a certain reaction is kkk = 3.50×10−3 s−1s−1 . If the initial reactant concentration was 0.450 MM, what will the concentration be after 19.0 minutes?
A zero-order reaction has a constant rate of 3.50×10−4 M/sM/s. If after 65.0 seconds the concentration has dropped to 3.50×10−2 MM, what was the initial concentration?

Answer 1

Explanation:

Question 1

Rate constant = 3.50×10−3 s−1

Initial Concentration [A]o =  0.450 M

Final concentration [A] = ?

time = 19 minutes = 1140 s (upon conversion to seconds)

Integrated rate law for a first order reaction is given as;

ln[A] = ln[A]o - kt

ln[A] = ln (0.450) - (3.50×10−3)1140

ln[A] = -0.799 - 3.99

ln[A] = -4.789

[A] = 0.0083M

Question 2

Rate constant, k = 3.50×10−4 M/s

time = 65 s

Final Concentration [A] = 3.50×10−2 M

Initial Concentration [A]o = ?

Integrated rate law for a first order reaction is given as;

[A] = [A]o - kt

[A]o = [A] + kt

[A]o = 3.50×10−2 + (3.50×10−4) * 65

[A]o = 3.50×10−2 + 0.02275

[A]o = 0.05775 M