Question

For the reaction: 2 A+B 3 C the rate of disappearance of B was 0.30 M/s. What is the rate of disappearance of A and the rate of appearance of C?

Answer 1

Answer:

rA = 0.60 M/s

rC = 0.90 M/s

Explanation:

Let's consider the following reaction:

2 A+B ⇒ 3 C

The rate of each substance can be calculated like the change in its concentration divided by the change in time. Given the rate must always be positive, we add a minus sign before the reactants change in concentration.

$rA=-\frac{\Delta[A] }{\Delta t}$

$rB=-\frac{\Delta[B] }{\Delta t}$

$rC=\frac{\Delta[C] }{\Delta t}$

The rate of the reaction is equal to the rate of each substance divided by its  stoichiometric coefficient.

$r= \frac{rA}{2} =\frac{rB}{1} =\frac{rC}{3}$

The rate of disappearance of B is 0.30 M/s.

The rate of disappearance of A is:

$\frac{rA}{2} =\frac{rB}{1}\\rA = 2 \times rB = 2 \times 0.30 M/s = 0.60 M/s$

The rate of appearance of C is:

$\frac{rB}{1} =\frac{rC}{3}\\rC = 3 \times rB = 3 \times 0.30 M/s = 0.90 M/s$