How many moles in 2.0g of carbon dioxide?

First you need to find out the Limiting reactant (LR). convert both reactants to the same thing. Check that the chemical equation is balanced.  Now use stoichiometr and remember at moles, multiply: need moles, divide2 g / 42g/mol=  0.0477 mol propane         mass propane/ Molar Mass propane = moles propane4 g / 32 g/mol= 0.125 mol oxygen X (1 mol/ 5 mol) = 0.025 mol propane   oxygen is the LRmass O2 / MM O2 X (mol propane / mol O2)0.025 mol X (3 mol / 1 mol ) = .075 mol CO20.075 mol X (12 + 2*16) g /mol = 3.6 g CO2 In one step:2 g / 42g/mol X (3 mol / 1 mol ) X 48 g/mol = 6.86 g CO24 g / 32 g/mol X (3 mol / 5 mol ) X 48 g/mol = 3.6 g CO2mass/ MM        X coefficient ratio  X MM (new)