plz check 2 percent yield problems for me, ty?

Question

3NO2 + H2O -> 2HNO3 + NO

If 74g of NO2 reacts with 100 g H20, 23 g gaseous NO are made. Calculate % yield.

Find Limiting Reagent
74 g NO2 (1 mole NO2 / 46 g NO2) = 1.61 mole NO2
100 g H2O (1 mole H2O / 18.02 g H2O) = 5.55 mole H2O
NO2 is the LR

Convert mole NO2 to g NO
1.61 mole NO2 (1 mole NO / 3 mole NO2) = 0.54 mole NO
0.54 mole NO (30 g NO / 1 mole NO) = 16.1 g NO

Percent Yield
23 g NO / 16.1 g NO * 100% = 142.9%

THE SECOND ONE IS
3NO2 + H2O -> 2HNO3 + NO

If 2.2 kg of NO2 reacts with 1.2 kg H2O, 0.23 kg gaseous NO are made. Calculate % yield.

Find LR
2200 g NO2 (1 mole NO2 / 46 g NO2) = 47.8 mole NO2
1200 g H2O (1 mole H2O / 18.02 g H2O) = 66.6 mole H2O
NO2 is the LR

Convert mole NO2 to g NO
47.8 mole NO2 (1 mole NO / 3 mole NO2) = 15.9 mole NO
15.9 mole NO (30 g NO / 1 mole NO) = 477 g NO

Percent Yield
230 g NO / 477 g NO * 100% = 48.2%

ty for your help!

Answer 1

Sorry but both of your answers are wrong.

In the first part you are right that NO2 is the limiting reagent, but by a much slimmer margin than you think. It takes 3 NO2 to react with 1 H2O. So you use 3*1.61 moles of NO2 to react with 1 mole of H2O. 3 times 1.61 is 4.83 so NO2 is still limiting (4.83 is less than 5.55). You need to keep stoichiometry in mind when you calculate yield too.

In the first case the % yield (based on NO2) is 100%

For the second part NO2 is no longer the LR. The limiting reagent is the H2O. 3*47.8 moles of NO2 is 143.4 moles of NO2 and you only have 66.6 moles of H2O. The water is limiting in the second case and affects the yield.

Good luck!

Answer 2

The second one is right. First one is not. Reality check - you can't get more than 100% theoretical yield.

3 mol NO2 make 1 mol NO, so

1.61mol NO2 x 1mol NO/3 mol NO2 = 0.54 mol NO

0.54 mol NO x 30 g/mol = 16.1 g NO

(16.1/23) x 100 = 70%