# What volume will a 300.0 mL sample of a gas at STP occupy when the pressure is doubled at constant temperature?

##### 1 Answer

#### Answer:

#### Explanation:

When *number of moles* and *temperature* are kept **constant**, pressure and volume have an **inverse relationship** - this is known as Boyle's Law.

In simple terms, when pressure **increases**, volume *decreases*, and when pressure **decreases**, volume *Increases*.

Mathematically, this is written as

#color(blue)(P_1V_1 = P_2V_2)" "# , where

So, if pressure **doubles**, what would you expect to happen to the sample's volume?

Well, the only way the product between the pressure and the volume would remain constant is if the volume would be **halved**.

Now, you don't need to know the *actual* values of the two pressures, all you need to know is the relationship that exists between them.

#P_2 = 2 * P_1#

This means that you have

#P_1V_1 = P_2V_2 implies V_2 = P_1/P_2 * V_1#

#V_2 = color(red)(cancel(color(black)(P_1)))/(2 * color(red)(cancel(color(black)(P_1)))) * V_1 = 1/2 * V_1#

#V_2 = 1/2 * "300.0 mL" = color(green)("150.0 mL")#