The rate constant for a second order reaction has the value of 2.5 x 10–3 L·mol–1·s–1. If the initial concentration of reactant is 3.5 mol·L-1, what will be the molar concentration of the reactant after 2.5 minutes?

[1/(A)] - [1/(Ao)] = kt

k is given in seconds; therefore, change 2.5 minutes to seconds.

I did that and but I got 1.52 mol/L rather 0.97 (as the answer key provides it)

I obtained 1.51 which is essentially the same as your answer. Did they give a reaction? The formula actually is

1/A - 1/Ao = akt so the a could change things but usually is not a number like 2/3. Must be a wrong answer. If you find to the contrary please be sure and post so I will know. However, I don't see anything wrong with what we've done.

No, they did not provide any reaction for this problem. If I'll find the solution, I'll post it here. Thank you for your help.

To determine the molar concentration of the reactant after 2.5 minutes, we can use the second order rate equation:

1/[A]t - 1/[A]0 = kt

Where:
[A]t is the molar concentration of the reactant at time t
[A]0 is the initial molar concentration of the reactant
k is the rate constant
t is the time

First, we need to convert the time from minutes to seconds:
t = 2.5 minutes x 60 seconds/minute = 150 seconds

Now, we can plug in the values into the rate equation:

1/[A]t - 1/[A]0 = k * t

Rearranging the equation, we get:

1/[A]t = 1/[A]0 + k * t

Substituting the given values:
1/[A]t = 1/3.5 mol·L-1 + (2.5 x 10–3 L·mol–1·s–1)(150 s)

Now we can solve for [A]t by taking the reciprocal of both sides:

[A]t = 1 / (1/3.5 mol·L-1 + (2.5 x 10–3 L·mol–1·s–1)(150 s))

Calculating the right side of the equation:

[A]t = 1 / (1/3.5 + 0.375)

Simplifying the expression:

[A]t = 1 / (1/3.875)

Taking the reciprocal:

[A]t = 3.875 mol·L-1

Therefore, the molar concentration of the reactant after 2.5 minutes is 3.875 mol·L-1.