A student is given a 5.000g sample to analyze composed of tin metal with a small amount of a zinc
impurity. The student dissolves the metal in concentrated nitric acid, allows the reaction to
continue to completion, and heats the mixture to leave 6.341g of solid containing only a tin oxide of
unknown composition and ZnO.
In order to separate the unknown tin oxide from the ZnO, the oxide mixture is dissolved in dilute
hydrochloric acid and treated with hydrogen sulfide. This precipitates the tin as SnS2. The
precipitate is filtered, dried, and weighed to a constant mass. The mass of the precipitate was
7.316g.
a) Calculate the mass percent of tin in the SnS2 precipitate.
b) Calculate the mass percent of tin in the original sample of metal.
c) Calculate the mass of the ZnO formed during the first reaction.
d) Calculate the mass of the tin oxide formed during the first reaction.
e) What is the empirical formula of the tin oxide formed during the first reaction? Justify your
answer.
f) Suppose that the student was unaware of the presence of the zinc impurity. Calculate the
percent yield that student would determine for the first reaction assuming no zinc is present.
g) Give one reason a student who is unaware of the zinc impurity might give for the percent yield
not being 100% that accounts for the results of your calculation in f). Explain your answer.
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