Question

Can some one show me a simple step by step solution to solve this. The book is very confusing.

Determine the amount of NH4Cl that will be formed from the 34.0 g of NH3. Remember to use significant figures and a unit in your answer (for example, 275 g).

Answer 1

Print these steps.
1. Write and balance the equation.
NH3 + HCl ==> NH4Cl (The problem doesn't say it reacts with HCl and you only need to know that 1 mol NH3 is in 1 mol NH4Cl but I think an equation makes it more obvious.)
2. Convert what you have, in this case NH3, into mols. mols NH3 = grams NH3/molar mass NH3. 34.0/17 = 2.0 mols
3 Using the coefficients in the balanced equation, convert mol of what you have (NH3) in mols of what you want (in this case NH4Cl).
2.0 mols NH3 x (1 mol NH4Cl/1 mol NH3) = 2.0 mols x 1/1 = 2.0 mols NH4Cl
4. Now convert mols of what you want (NH4Cl) to g. g = mols NH4Cl x molar mass NH4Cl = 2.0 x about 53.5 = about 107.0 g NH4Cl.
Then you look at the only number given in the problem (34.0g) and that has three significant figures so the answer is allowed 3 s.f. Therefore, round that 107.0g number to 107. By the way I have estimated the numbers throughout the problem; you need to go through and do them more accurately. The molar mass NH4Cl also was estimated.
This 4-step procedure will work all simple stoichiometry problems (not limiting reagent problems---they require an extra step or two).

Answer 2

Don't forget to make that 107 g.