When carbon is burned in air, it reacts with oxygen to form carbon dioxide. When 20.4 g of carbon were burned in the presence of 71.1 g of oxygen, 16.7 g of oxygen remained unreacted. What mass of carbon dioxide was produced?

Question

Express your answer to three significant figures and include the appropriate units.

Answer 1

C + O2 ---> CO2

Mols of C
20.4 /12 g/mol = 1.7 mol of C
result is 1.7 mol of CO2
C = 12
O2 = 32
CO2 = 44 g/mol

1.7 mol * 44 g/mol = 74.8 grams

Answer 2

How much heat is evolved if 2 moles of C3H8 is burned?