Question

Effect of increase in temperature for distribution of molecular speeds of gas is?

• Area under the distribution curve remains constant
• Fraction of molecules with most probable speed increases
• Most probable speed increases

Solution

The following is the distribution of gas molecules with speed.

The most common mistake we make is to misinterpret the question. Here the options are comparing the value of all the options before and after the temperature has been increased.

When we the temperature is increased the most obvious reaction is that most probable speed increases as it is given by sqrt((2RT)/M)

So option D is correct.

If the temperature is increases the number of molecules of gas remains same because we are not adding any gas and no reaction takes place.

As shown the temperature is increased the peak which is the most probable velocity increases shifts to right but the number of molecules at the most probable speed decreases.

So option B is incorrect.

The height of the graph is decreasing. But the number of molecules is same, so the area under the graph is same. Hence the graph becomes broader.