How many grams of water can be formed from the reaction between 10 grams of oxygen and 1 gram of hydrogen?
A)11 grams of water are formed since mass must be conserved.
B)10 grams of water are formed since you can't get a greater mass of water produced than oxygen reacting.
C)9 grams of water are formed because oxygen and hydrogen react in an 8:1 ratio.
D)No water is formed because there is insufficient hydrogen to react with the oxygen.

Question

Quizplus · Accepted Answer

The balanced equation for the reaction between oxygen and hydrogen to form water is: 
2H2 + O2 -> 2H2O 
This shows that 2 moles of hydrogen react with 1 mole of oxygen to produce 2 moles of water. To find the mass of water produced, we need to first find the limiting reactant. 
10 grams of oxygen is equal to 0.31 moles (using the molar mass of oxygen). 
1 gram of hydrogen is equal to 0.98 moles (using the molar mass of hydrogen). 
Since we have more moles of hydrogen than oxygen, oxygen is the limiting reactant. 
1 mole of oxygen produces 2 moles of water, so 0.31 moles of oxygen will produce 0.62 moles of water. 
The mass of 0.62 moles of water is 11.16 grams (using the molar mass of water), so 9 grams of water cannot be formed, but 11.16 grams of water can be formed. Therefore, the best choice is C, which states that 9 grams of water are formed.

How Many Grams of Water Can Be Formed from the Reaction