Question

If 20 grams of Zinc phosphate reacts with excess hydrochloric acid and produces 18 grams of Zinc chloride what is the percent yield?
Zn3(PO4)2 + 6HCl —> 3ZnCl2 + 2H3PO4

Answer 1

Answer:

$Y=85\%$

Explanation:

Hello!

In this case, since we know the balanced chemical reaction, we are first able to realize there is a 1:3 mole ratio between zinc phosphate and zinc chloride; it means that we can first compute the moles of the desired product via stoichiometry:

$n_{ZnCl_2}=20gZn_3(PO_4)_2*\frac{1molZn_3(PO_4)_2}{386.11gZn_3(PO_4)_2}*\frac{3molZnCl_2}{1molZn_3(PO_4)_2}=0.16gZnCl_2$

Next, since those moles are associated with the theoretical yield of zinc chloride, we obtain the corresponding mass:

$m_{ZnCl_2}^{theoretical}=0.16molZnCl_2*\frac{136.29gZnCl_2}{1molZnCl_2} =21gZnCl_2$

Finally, we compute the percent yield by diving the actual yield (18 g) by the theoretical yield:

$Y=\frac{18g}{21g}*100\%\\\\Y=85\%$

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