Question

I don't understand how to answer this questions. I thought molecular weight was adding up the atomic weight of each element in a molecule...?

If a 0.614g sample of a gas maintains a pressure of 238 mmHg when contained in a 1.0L flask at 0.0 degree Celcius, what is the gas's molecular weight?

Answer 1

You're right but there are other ways to obtain the molecular weight than adding up the atomic weights of each element.
In this case, PV = nRT is the universal gas equation.
You know P (change to atmospheres), You know V (in liters), you know R and you know T(must be in Kelvin and note the correct spelling of celsius). The only unknown in this equation is n, the number of moles of the gas.
Then mols gas = grams/molecular weight. You know mols from the calculation, you know grams from the problem, calculate molecular weight.