Chemistry
posted by anonomous .
Using molar volume (STP) or the ideal gas law equation, determine the molar mass, g/mole, of each of the following:1.)11.1g of a gas that has a volume of 1.50L at STP. 2.) 0.742g of a gas that has a volume 860mL at 1.28atm and 18∘C. 3.) 2.42g of a gas that has a volume 1.88L at 695mmHg and 19∘C.

1)
Use PV = nRT and solve for n = number of mols of the gas. Then n = grams/molar mass gas. You know grams and n, solve for molar mass.
I think the others are done the same way. 
How are we suppose to solve for the molar mass because we don't have the chemical formula for the gas?

Read my response again. I told you how.
You use PV = nRT and solve for n = number of mols. Then n = grams/molar mass. You have n from the PV = nRT and you have grams from the problem. Substitute those and solve for molar mass of the gas. You're making it harder than it is. Don't get intimidated by chemistry.