Question

Limiting reactants! Could someone please explain it with these questions?
1. 4.04g of hydrogen gas is exploded with 16.00g of oxygen. What is the limiting reactant? (Please explain how you got to the answer!)
2. 2C7H6O3 + C4H6O3 --> 2C9H8O4 + H2O
13.80g of C7H6O3 reacts with 10.26g of C4H6O3. What is the limiting reactant (again with explanation please!)? Thank you for any help :)

Answer 1

For the first question, assume H2O would be formed from the reaction.
First, balance the equation.
H2 + O2 -> H2O
=> 2H2 + O2 -> 2H2O

So, for complete reaction, one mole of O2 requires 2 moles of H2.
No. of mole of O2 = 16.00/(16.0x2) = 0.5 mole
No. of mole of H2 = 4.04/(1.0x2) = 2.02 moles

Since 0.5mole of O2 only needs 1.0 mole of H2 for complete reaction, and we have 2.02 moles of H2 here. So, H2 is in excess. In other words, O2 is the limited reactant.

I think you can try the second one yourself!

Answer 2

Thank you!! This is the bit where I get stuck, you see, the bit I don't understand is where 0.5mole of O2 only needs 1.0 mole of H2 for complete reaction. How do you know this piece of info?

Answer 3

From the reaction equation.
Look at the coefficients there!