Answer:
Oxygen is the excess reactant.
Explanation: A simple balanced chemical equation for the production of water, will show:
2H2 + O2 -----> 2H20
2 : 1 2
From this, we can see that 2 moles H2 react with 1 mole of O2 to produce 2 moles of H2O. That is to say, hydrogen reacts with oxygen in the ratio 2:1
Also if 1 mole of H2 is needed to produce water, it will require 1/2 mole of O2 to react with.
Since we know this, we can tell from our question that 1 mole of H2 will react with 1/2 mole of O2 and be left with 1/2 mole of O2 as excess.
We can have a chemical equation for this as:
1/2H2 + O1/2 ------> 1/2H2O
1 : 1/2
Therefore, the H2 can be said to be the limiting reactant (gets consumed when the reaction is completed) while the oxygen is the excess reactant.
