A 7.25 g portion of an unknown white crystalline solid is analyzed
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A 7.25 g portion of an unknown white crystalline solid is analyzed. Elemental analysis yields 2.64 g of calcium and 4.61 g of fluorine.
Answer the following questions to determine whether the solid should be considered a pure substance or a mixture.
(a) Calculate the simplest whole-number ratio of calcium atoms to fluorine atoms present in the solid.
(b) Write the empirical formula that corresponds to the ratio determined in part (a).
(c) A reference source lists calcium fluoride as the only binary compound of calcium and fluorine. Discuss whether the analytical data are consistent with the unknown being a single pure compound of calcium and fluorine.
(d) Based on your reasoning in part (c), state whether the original 7.25 g sample is best described as a pure substance or a mixture, and justify your conclusion.