A 18.50 gram sample of a gas exerts a pressure of 2.40 atmospheres when held in an 7.00 liter at 25.0 °C. What is the molar mass of the gas?

Question

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Answer 1

PV = nRT

pressure * volume = #moles * gas constant * temp (in K, where K=C+273)

**be sure to use the correct gas constant: pay attention to your units to know which one you need

in this case, units include liters and atmospheres, so will need

the R value with unit (L*atm*K^-1*mol^-1), which is 0.08206

1) Find out what you can:

Find # moles

2.40 atm * 7.00L = n * 0.08206 L*atm * 298K

mol * K

n = 0.687 moles

2) Use new values to help with creating answer:

Knowing #moles & total mass, find molar mass (g/mol)

18.5g = 26.9 g/mol

0.687mol