Answer to Question #255741 in General Chemistry for Emre

Question

Three pure compounds form when 1.50 g samples of element X combine with, respectively, 0.708 g, 0.945 g and 1.184 g of element Z. The first compound has the formula X₂Z₃. Find the empirical formulas of other two compounds.

Answer 1

Mass of X in 1st compound = 1.0 g

Mass of Z in 1st compound = 0.472 g

The emperical formula of first compound = X₂Z₃

That means 1.0 g of X is equivalent to 2 moles of X

<=> 1 mole of X = 0.5 g of X.

0.472 g of Z is equivalent to 3 moles of Z

<=> 1 mole of Z = 0.15733 g of X

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2nd compound

Mass of X = 1.0 g

So moles of X = 1.0/0.5 = 2

The mass of Z = 0.420 g

Number of moles of Z = 0.420/0.15733 = 2.6695 moles

Ratio of moles of X to Z = 2:2.6695 = 3:4

Answer: Emperical formula of second compound = X₃Z₄

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3rd compound

Mass of X = 1.0 g

So moles of X = 1/0.5 = 2 moles

The mass of Z = 0.236 g

Number of moles of Z = 0.236/0.15733 = 1.5 moles

Ratio of moles of X to Z = 2:1.5 = 4:3

Emperical formula of third compound = X₄Z₃