Question

0.175 g of a gas occupies 242.0 mL at STP. What is its molecular weight?

Answer 1

WE will assume here that the gas is ideal.

For ideal gas the realtion between pressure temperature and moles and volume is

PV = nRT

P = Pressure (Given STP ) = 1 atmosphere

n = moles = Mass / Molecular weight = 0.175 / Molecular weight

V = Volume = 242 mL = 0.242 L

T = Temperature = 273.15 Kelvin (STP)

R = gas constant = 0.0821 L atm / K mole

Putting all the values

1 X 0.242 = 0.175 X 0.0821 X 273.15 / Molecular weight

So molecular weight = 0.175 X 0.0821 X 273.15 / 0.242 = 16.21 g / moles

The possibility is that the gas is oxygen.