Please help with this limiting reactant problem. thank you?

Question

When 4.47 g of compound A (molar mass = 120.0 g) reacts with a few grams of compound B (molar mass unknown), 6.21 g of product C is produced. Analysis shows that C is actually a simple addition compound (that is, AB) and that the yield of product was 84.1% based on A. If A is the limiting reagent, what is the least amount of B that must be used to prepare the maximum amount of C obtainable from 4.47 g of compound A?

Answer 1

In 6.21 g of product C, the contributed mass from A is:
4.47g * 84.1% = 3.76g.
Hence the contributed mass from B is:
6.21g - 3.76g = 2.45g
If we are looking for a complete reaction of 4.47g A to form C, the least amount of B that must be used to prepare the maximum amount of C obtainable from 4.47 g of compound A is:
2.45g / 84.1% = 2.91g

Answer 2

check out the balanced equation: do no longer worry with reference to the products - focus in basic terms on the reactants: 4 mol NH3 reacts with 5 mol O2 the 1st certainty which you already know is that mol O2 must be > mol NH3 you have a million mol NH3 and a million mol O2 - so the O2 is proscribing because of the fact this is not > mol NH3 Divide The reactants of the balanced equation by using 5 0.8 mol NH3 + a million mol O2 in case you react a million mol O2 ( which you do) then you definately will react 0.8 mol NH3 , 0.2 mol NH3 will stay unreacted So precis : O2 is proscribing and 0.2 mol NH3 stay: Does this in effective condition any of the recommendations: confident determination 2) is genuine.