# A gas has a volume of 350 mL at 45°C. If the volume changes to 400 mL, what is the new temperature?

May 19, 2016

28°C.

#### Explanation:

The correct equation to use with these kinds of questions is the Combined Gas Law.

$\frac{{P}_{1} \cdot {V}_{1}}{T} _ 1 = \frac{{P}_{2} \cdot {V}_{2}}{T} _ 2$

This equation, though, is a little unnecessary at times because of the possibility of extra constants.

In this case you have a pressure constant which enables us to shorten your longer equation down to Charles' Law because pressure remains the same and doesn't affect the calculation.

$\frac{{V}_{1}}{T} _ 1 = \frac{{V}_{2}}{T} _ 2$

The next step is to isolate the variable that you want, which is, in this case, ${T}_{2}$.

${T}_{2} = \frac{{V}_{1} {T}_{1}}{V} _ 2$

Now it is time to replace your known variables with numbers

T_2 = (350mL*45°C)/(400mL)

And calculate...

T_2 = 28.125°C

Significant digits...

T_2 = 28°C