Question

1)

Ammonia reacts with  to form either  or  according to these unbalanced equations:

In a certain experiment 2.00 moles of  and 10.00 moles of  are contained in a closed flask. After the reaction is complete, 6.60 moles of  remains. Calculate the number of moles of  in the product mixture: (Hint: You cannot do this problem by adding the balanced equations, because you cannot assume that the two reactions will occur with equal probability.)

mol

2)

The aspirin substitute, acetaminophen (), is produced by the following three-step synthesis:

The first two reactions have percent yields of 85% and 93% by mass, respectively. The overall reaction yields 10 moles of acetaminophen product for every 13 moles of   reacted.

What is the percent yield by mass for the overall process?

Percent yield =    %

What is the percent yield by mass of Step III?

Percent yield =  %

3)

Zinc and magnesium metal each reacts with hydrochloric acid to make chloride salts of the respective metals, and hydrogen gas. A 10.10-g mixture of zinc and magnesium produces 0.6766 g of hydrogen gas upon being mixed with an excess of hydrochloric acid. Determine the percent magnesium by mass in the original mixture.

% Mg

Answer 1

Data insufficient for (1) and (2); please furnish the missing data.

(3) Let the mixture contain x g Zn; therefore, mass of Mg in the mixture = (10.10 – x) g.

Write down the balanced chemical equations for the reactions.

Zn + 2 HCl -------> ZnCl₂ + H₂

Mg + 2 HCl -------> MgCl₂ + H₂

As per the stoichiometric equations,

1 mole Zn = 1 mole Mg = 1 mole H₂.

Moles of Zn in the mixture = x/65.38 mole; moles of Mg in the mixture = (10.10 – x)/24.305 mole.

Molar mass of H₂ = 2*1.008 g/mol = 2.016 g/mol; moles of H₂ produced = (0.6766 g)/(2.016 g/mol) = 0.335615 mole.

Therefore,

x/65.38 + (10.10 – x)/24.305 = 0.335615

====> x/65.38 + 0.415552 – x/24.305 = 0.335615

====> 0.079937 = 41.075x/65.38.24.305

====> x = 3.0925

Therefore, percent Mg = (10.10 – 3.0925) g/(10.10 g)*100 = 69.38% (ans).