2H2 + O2à2H2O
How many water molecules are created when 32 grams of oxygen react completely with 4 grams of hydrogen?
A. 2
B. 20
C. 6.02 × 1023
D. 1.2 × 1024
A. 2 because for every 2 hydrogen atoms, there is 1 oxygen atom in water. If you have 4 hydrogen atoms, only 2 oxygen atoms can completely react with them.