Boyle's Law and Avogadro's Law

Chapter 11 Section 2 Gas Laws

Boyle's Law: Pressure and Volume

Robert Boyle (1627-1691), a British chemist, used a simple j-tube apparatus to experimentally compress air in the closed-end of a tube. As he added Mercury to the open end, the weight of the mercury compressed air trapped at the closed-end. The temperature was kept constant.

Boyle's Findings

• If the pressure on a gas increases, its volume decreases proportionately.

• If the pressure on a gas decreases, its volume increases proportionately.

Boyle's Findings (continued)

• If the volume of a gas increases, its pressure decreases proportionately.

• If the volume of a gas decreases, its pressure increases proportionately.

Inverse Relationship

Because the changes in pressure and volume are always opposite and proportional, the relationship between pressure and volume is an inverse proportion. Boyle's law states that the pressure and volume of a gas at constant temperature are inversely proportional. When one goes up the other must go down.

Multiple Choice

According to Boyle's Law, a trapped gas at constant temperature will _____________ in volume if the pressure is decreased.

• decrease

• increase

• not change

Boyle's Law: Finding Volume 

If a container of gas with a volume of 0.78 L breaks at a pressure of 9.00 atm, what would be the volume of the gas in the container at 1.00 atm?
 $P_1V_1\ =\ P_2V_2$  

 $\frac{P_1V_1}{P_2}$  =  $V_2$  

 $V_2$  =  $\frac{\left(0.78\ L\right)\left(9.00\ atm\right)}{\left(1.00\ atm\right)}$  

 $V_2$   = 7.02 L

Multiple Choice

At one sewage treatment plant, bacterial cultures produce 1000 L of methane gas per day at 1.0 atm. What volume tank would be needed to store one day's production at 5.0 atm?

• 200 L

• 2000 L

• 5000 L

End

Complete the practice problems on the Boyle's Law Worksheet.