If 28.0 g of methane gas (#CH_4#) are introduced into an evacuated 2.00-L gas cylinder at a temperature of 35°C, what is the pressure inside the cylinder?

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Answer 1 · 2016-02-22T03:43:09

The pressure of the methane gas will be 22.2 atm.

Use the ideal gas law with the formula #PV=nRT#, where #n# is moles, #R# is the gas constant, and #T# is temperature in Kelvins.

Determine the mole of #"CH"_4"# by dividing the given mass by its molar mass, #"16.04246 g/mol"# https://pubchem.ncbi.nlm.nih.gov/compound/297

#28.0cancel"g CH"_4xx(1"mol CH"_4)/(16.04246cancel"g CH"_4)="1.7454 mol CH"_4"#

Ideal Gas Law

Given/Known
#V="2.00 L"#
#n="1.7454 mol"#
#R="0.082057338 L atm K"^(-1) "mol"^(-1)#
#T="35"^@"C"+273.15="308 K"#

Unknown
Pressure, #P#

Solution
Rearrange the formula to isolate #P#. Substitute the given values into the formula and solve.

#PV=nRT#

#P=(nRT)/V#

#P=((1.7454"mol") xx (0.082057338"L atm K"^(-1) "mol"^(-1)) xx (308"K"))/(2.00"L")="22.2 atm"# rounded to three significant figures