A gas occupies 100.0 mL at a pressure of 780 mm Hg. What is the volume of the gas when its pressure is increased to 880 mm Hg?

1 Answer
Apr 23, 2017

Answer:

This question has been set by someone who has never used a mercury manometer............we gets #V_2=87.6*mL#

Explanation:

One atmosphere of pressure will support a column of mercury that is #760*mm# high. A manometer is thus a highly visual measure of the strength of a vacuum, or as a measure of atmospheric pressure.

If you put the column under a pressure greater than #1*atm# you are likely to get mercury all over the laboratory, where it will inhabit every crack and every cranny. This is a MAJOR cleanup job, which contract cleaners would not touch.

And so #P_1="780 mm Hg"/("760 mm Hg"*atm^-1)=1.026*atm.#

And so #P_2="880 mm Hg"/("760 mm Hg"*atm^-1)=1.158*atm.#

And now we use old #"Boyle's Law"#, #P_1V_1=P_2V_2.....#, and solve for

#V_2=(P_1V_1)/P_2=(1.026*atmxx100.0*mL)/(1.158*atm)#

#=87.6*mL#

The volume is slightly decreased, as we would expect, why?