Chemistry help for finals

Question

the combustion of propane is c3h8(g)+5o2(g)→3co2(g)+4h2o(g) how many grams of water do you expect to produce

Answer 1

Using the balanced chemical reaction equation:

C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g)

If you start with 27.3 g of C₃H₈(g), first convert this to the number of moles of C₃H₈(g) by dividing by the molar mass. The molar mass of C₃H₈ is calculated by using the atomic mass of carbon found in the Periodic Table (carbon = 12.011 g/mol) and the hydrogen (hydrogen = 1.008 g/mol) so the molar mass is (3)(12.011) + (8)(1.008) = 44.097 g/mol.

(27.3 g)/(44.097 g/mol) = 0.61909 moles of C₃H₈(g)

The chemical reaction equation says that for every 1 mole of C₃H₈(g) reacted, 4 moles of H₂O(g) is produced. So the number of moles of H2O produced is (0.61909)(4) = 2.476 moles. Now use the molar mass of H₂O to convert this to grams. The molar mass is (2)(1.008) + (1)(15.999) = 18.015 g/mol.

(2.476 mol)(18.015 g/mol) = 44.6 g H₂O