molecular weight

[akekilova]

I need to calculate what volume of oxygen would be required to burn 100 g of propane.
I've got that it is 363,64 g of O₂ for 100g of C₃H₈

then I use Ideal gas law to find the volume V= nRT/P
n= 363,64 g /32 g/mol
here is a question. We need 5 moles of oxygen for 1 mole of propane. Should I calculate n with 32 g/mol of O₂ or I need 5O₂=160 g/mol

Please advice

[expert]

Molar volume of any gas at normal conditions is 22,4 L. That's the law. To find the volume of 5 mols of oxygen just simply multipy 5x22,4