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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: ibstudent on February 01, 2012, 03:58:04 AM

Title: Rearranging the Ideal Gas Law Equation
Post by: ibstudent on February 01, 2012, 03:58:04 AM

Hi!

Attached is a question I really don't understand which involves the rearrangement of the ideal gas law equation... the mark scheme is also attached...

As far as I know, Mr is not included in the ideal gas law equation, so where did it come from????

If anyone could clear my doubt, I will very much appreciate it  :)

Title: Re: Rearranging the Ideal Gas Law Equation
Post by: UG on February 01, 2012, 04:06:13 AM

They substituted 'n' for 'm/M'

Title: Re: Rearranging the Ideal Gas Law Equation
Post by: Nisarg Shah on February 06, 2012, 12:58:06 AM

Quote from: ibstudent on February 01, 2012, 03:58:04 AM

As far as I know, Mr is not included in the ideal gas law equation, so where did it come from????

PV=nRT
Since n is number of moles, which is defined as given mass/molecular mass.
PV=(m/M)RT, where m stands for given mass and M stands for molecular mass.

Title: Re: Rearranging the Ideal Gas Law Equation
Post by: billnotgatez on February 06, 2012, 06:45:12 AM

I think the original question is what is the meaning of
M_r

M sub r
rather than just
M

Title: Re: Rearranging the Ideal Gas Law Equation
Post by: Borek on February 06, 2012, 07:55:19 AM

M_r is just another symbol for molar mass.