Answer to Question #144452 in General Chemistry for zaina

Question

When 15g of Hydrogen is combined with 12g of Oxygen, 20g of water formwith extra Oxygen left over. What is the mass of the excess Oxygen?

Answer 1

2H2 + O2= 2H2O

The limiting reagent here is O2, therefore H2 and not O2 will be in excess

No of moles of H2 = 15/4 = 3.75 moles

No of moles of O2 =12/32= 0.375

Only 2×0.375 moles of H2 will react with 0.375mole of O2

No of moles of H2 that will react is 0.75

No of excess mol= 3.75-0.75 = 3moles of H2

1 mole of H2 is 2g

3 moles of H2 = 3×2= 6g of H2 in excess