Question

Given an initial cyclopropane concentration of 0.00560 m, calculate the concentration of cyclopropane that remains after 1.50 hours.

Answer 1

We can solve this problem by assuming that the decay of cyclopropane follows a 1st order rate of reaction. So that the equation for decay follows the expression:

A = Ao e^(- k t) 

Where,

A = amount remaining at time t = unknown (what to solve for) 
Ao = amount at time zero = 0.00560 M 
k = rate constant
t = time = 1.50 hours or 5400 s 

The rate constant should be given in the problem which I think you forgot to include. For the sake of calculation, I will assume a rate constant which I found in other sources:

k = 5.29× 10^–4 s–1                     (plug in the correct k value)

Plugging in the values in the 1st equation:

A = 0.00560 M * e^(-5.29 × 10^–4 s–1 * 5400 s )

A = 3.218 × 10^–4 M           (simplify as necessary)