Question

A sample of gas collected at 685 mm Hg occupies 131 mL. At constant temperature, what pressure does the gas exert if the volume increases to 478 mL? a. 188 b. 1320 c. 128 d. -88.8

Answer 1

a. P=188mmHg

Step-by-step explanation:

A gas undergoing a change of volume and pressure at constant temperature (and not changing the number of molecules), follows Boyle's Law:
`P_1V_1=P_2V_2`

The units of these quantities can be any measure of pressure and volume, so long as long as the units are the same between beginning and ending conditions.

Substitute and solve:

`P_1V_1=P_2V_2`

`(685[mmHg])(131[mL])=P_2(478[mL])`

`\frac{(685[mmHg])(131[mL\!\!\!\!\!\!\!\!\!{--}])}{478[mL\!\!\!\!\!\!\!\!\!{--}]}=\frac{P_2(478[mL]\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!{----})}{478[mL] \!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!{----}}`

`187.730125523[mmHg]=P_2`

Accounting for significant figures,
`P_2=188[mmHg]`