# Question #4ee02

##### 1 Answer

It can be solved like this:

#### Explanation:

1.

This is not a well worded question since the rate of the reaction is not constant. I will assume they are asking for the average rate after 40 min.

Average rate = loss of sulfur / time

Average rate =

2.

There are several methods you could use to show this. I will use "The Integral Method".

For a 1st order reaction we have:

Where **k** is the rate constant.

This can be expressed in terms of the rate of disappearance of *A* :

Rearranging and applying integration between 0 and t gives:

This gives:

This means that if the reaction is 1st order then a plot of **t** should be a straight line of the form

The gradient of the line will be equal to **-k.**

Excel is a useful tool to do this (other spreadsheet programmes are available) . Here's what I got:

The straight line confirms that the reaction is 1st order.

Since

The equation of the line has been added by the programme for you:

This tells us that

3.

We now have the rate equation for the reaction:

Rate =

At the 30th minute the %S = 0.47