Question

suppose 16.0g of benzene C6H6 is burned in oxygen.What mass of O2 is required for the complete combustin

Answer 1

first we write the chemical equation:
C6H6 + O2 -> CO2 + H2O
then we balance this:
2C6H6 + 15O2 -> 12CO2 + 6H2O
then we solve for the molecular weight of C6H6. Note that mass of C = 12 and H = 1. thus,
6*12 + 6*1 = 78 g/mol
then we get the number of moles of C6H6 used in the reaction:
n = 16/78 = 0.205 moles

then we use stoich ratio from thethe equation to get moles of O2:
0.205 * (15 mol O2 / 2 mol C6H6) = 1.5375 mol O2
note: molecular mass of O2 = 32 g/mol
finally,
1.5375 * 32 = 49.2 g O2