Question

If the initial concentration of A is 0.00230 M, what will be the concentration after 485 s?

How do you know in general what type of order reactions is it (zero, first, second) when it comes to word problems?? also, can I get step by step on how to solve?

Answer 1

Answer: Here the Order of the reaction is predicted by the units of the rate constant .

For a zero-order reaction, the rate of reaction is a constant. When the limiting reactant is completely consumed, the reaction abrupts stops.

Differential Rate Law:   r = k

The rate constant, k, has units of mole L^-1 sec^-1.

2] For a first-order reaction, the rate of reaction is directly proportional to the concentration of one of the reactants.

Differential Rate Law:   r = k [A]

The rate constant, k, has units of sec^-1.

3] For a second-order reaction, the rate of reaction is directly proportional to the square of the concentration of one of the reactants.

Differential Rate Law:   r = k [A]²

The rate constant, k, has units of L mole^-1 sec^-1.

Here , According to the question we have given the rate constant unit M^-1 S^-1 Means it is a second order reaction .

Now we have to use the second order reaction which is :

1/[A] -1/[A⁰] = Kt

Here [A⁰] is a initial concentration , [A] is final concentration , K is rate constant and t is time

1/[A] = [0.990 * 485 ] + 1 / 0.00230

1/[A] = 480.15 + 434.782 = 914.932

[A] = 0.001093 M

Hence the final concentration is 0.001093 M . It is all about the given question thnak you :)