Question

A sample of gas is placed in a 250 mL flask, where it exerts a pressure of 70.7 mmHg. What is the pressure of the gas if it is transferred and sealed within a 125 mL flask?

Answer 1

Well, is not `P_1V_1=P_2V_2`...?

Explanation:

...and this is old `"Boyle's Law....."`

We solve for `P_2=(P_1V_1)/V_2`

`-=(70.7*mm*Hgxx250*mL)/(125*mL)=141.4*mm*Hg`

So the pressure HALVES if the volume doubles, and DOUBLES if the VOLUME halves....

Note that a mercury column is a good, practical way of measuring pressure....here the units cancel away...we know that `1*atm` will support a column of mercury that is `760*mm` high...

And so `760*mm*Hg-=1*atm`...

These days mercury manometers have all BUT disappeared in even undergraduate laboratories. I could not get permission to set one up in an A2 lab (well, I could, but I could not invest the time to do so).