0.54 g
Lookup the atomic weights of oxygen and hydrogen. Atomic weight oxygen = 15.999 Atomic weight hydrogen = 1.00794 Calculate molar masses Molar mass O2 = 2 * 15.999 = 31.998 g/mol Molar mass H2O = 2 * 1.00794 + 15.999 = 18.01488 g/mol Now determine how many moles of O2 you have 2.1 g / 31.998 g/mol = 0.065629102 mol Balance the equation so you get as the balanced equation, 2 C4H6(g) + 11 O2(g) → 8 CO2(g) + 6 H2O(g) Looking at the balanced equation, for every 11 moles of O2 consumed, 5 moles of H2O are produced. So divide the number of moles of O2 you have by 11, then multiply by 5, giving: 0.065629102 mol / 11 * 5 = 0.02983141 mol And finally, multiply by the molar mass of H2O, so 0.02983141 mol * 18.01488 g/mol = 0.53740927 g Round the results to 2 significant figures getting 0.54 g