Limiting reactant / reagent questions. Show work as well as explanation please. Thank you !?

Question

1. Consider the reaction:

2H2 + O2 --> 2H2O

(The second, third, and fifth 2's are subscripts.)

Identify the limiting reagent in each of the reaction mixtures given below:

a. 50 molecules of H2 and 25 molecules of O2.

b. 0.8 mol H2 and 0.75 mol O2.

c. 5 g H2 and 56 g O2.

(All 2's following an H or O are subscripts.)

2. Ammonia is produced form the reaction of nitrogen and hydrogen according tot eh following balanced equation:

N2 + 3H2 --> 2NH3

(The first and second 2 as well as the last 3 are subscripts.)

a. What is the maximum mass of ammonia that can be produced from a mixture of 1000 g N2 and 500 g H2?

(All 2's are subscripts.)

b. What mass of which starting material would remain unreacted?

Answer 1

a no reactant is in excess

b H2 is the limiting reactant

c Moles H2 = 5 g/ 2 = 2.5

moles O2 = 56 / 32 = 1.75

H2 is the limiting reactant ( 1.75 x 2 = 3.5 moles of H2 are needed)

Moles N2 = 1000 g / 28 g/mol =35.7

moles H2 = 500 g/ 2 g/mol = 250 ( in excess)

moles NH3 = 35.7 x 2 =71.4

mass NH3 71.4 mol x 17 g/mol =1213.8 g

moles H2 needed = 35.7 x 3 =107.1

moles H2 in excess = 250 - 107.1 =142.9

mass H2 = 142.9 mol x 2 g/mol =285.8 g