# Boyle's Law Formula

Boyle's Law shows the relationship between the Pressure and Volume of a gas. Pressure and volume have a direct relationship, so if the volume goes up then the pressure goes down and if the pressure goes up then the volume goes down (and vice versa)

The equation for Boyle's Law is:

*P _{1}V_{1} = P_{2}V_{2}*

*P _{1}* = Initial Pressure (

*atm or mmHg*)

*V _{1}* = Initial Volume (

*L or mL*)

*P _{2}* = Final Pressure (

*atm or mmHg*)

*V _{2}* = Final Volume (

*L or mL*)

*Note:* The units of pressure and volume do not matter however the units much match for both P_{1} and P_{2} and for V_{1} and V_{2}.

Boyle's Law Formula Questions:

1.) A balloon contains 7.2L of He. The pressure is reduced to 2.00atm and the balloon expands to occupy a volume of 25.1L. What was the initial pressure exerted on the balloon?

Answer: For this problem the Initial Volume is *V _{1}* = 7.2

*L*. We are asked to find the Initial Pressure (

*P*). The Final Pressure is

_{1}*P*= 2.00

_{2 }*atm*and the Final Volume is

*V*= 25.1

_{2}*L*.

Plug into the Boyle's Law Equation

*P _{1}V_{1} = P_{2}V_{2}*

*P _{1}*(7.2

*L*) = (2.00

*atm*)(25.1

*L*)

*P _{1}* = 6.97

*atm*

The initial pressure exerted on the balloon was 6.97atm.

2.) 352mL of chlorine under a pressure of 680 mmHg are placed into a container under a pressure of 1210 mmHg. The temperature remains constant at 296K. What is the volume of the container?

Answer: The Initial Volume is *V _{1}* = 352

*mL*. The Initial Pressure is P

_{1}= 680 mmHg. The Final Pressure is

*P*= 1210

_{2}*mmHg*. The Final Volume (

*V*) is what we are trying to find in the problem.

_{2}Plug into the Boyle's Law Equation

*P _{1}V_{1} = P_{2}V_{2}*

(680 *mmHg*)(352 *ml*) = (1210 *mmHg*)( *V _{2}*)

*V _{2}* = 197.82

*mL*

The volume of the container would be 197.82 *mL*