Question

2H2 (g) + O2 (g) = 2H2O (g) What is the limiting reagent in each of the following reactions? 1) 50 molecules of H2 and 25 molecules of O2? 2) 100 molecules of H2 and 40 molecules of O2 ? 3) 100 molecules of H2 and 100 molecules of O2 ? 4) 0.50 mol H2 and 0.75 mol O2? 5) 0.80 mol H2 and 0.75 mol O2? 6) 1.0 g H2 and 0.25 mol O2 7) 5.00 g H2 and 56.00 g O2

Answer 1

2H2 (g) + O2 (g) = 2H2O (g)

for each molecule of O2 there are 2 molecules of H2 needed.

1) 50 molecules of H2 and 25 molecules of O2?

there is no limiting reaent, Both will react completely.

2) 100 molecules of H2 and 40 molecules of O2 ?

Here, H2 present in excess (for 40 molecules of O2, H2 needed is 80). imiting reagent is O2.

3) 100 molecules of H2 and 100 molecules of O2 ?

Here, H2 is limiting reagent (O2 present in excess)

4) 0.50 mol H2 and 0.75 mol O2?

H2 is limiting reagent ( for 0.50 moles of H2, O2 needed = 1/2 x 0.5 = 0.25, SO O2 present in excess)

5) 0.80 mol H2 and 0.75 mol O2?

H2 is limiting reagent ( for 0.80 moles of H2, O2 needed = 1/2 x 0.8 = 0.40 So, O2 present in excess)

6) 1.0 g H2 and 0.25 mol O2

O2 is limiting reagent (H2 is excess)

7) 5.00 g H2 and 56.00 g O2

no. of moles of H2 =5/2 = 2.5 moles

O2 moles = 56 / 32 = 1.75

H2 is limiting reagent