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Chapter 3: Problem 36

Selenium, an element used in the manufacture of photoelectric cells and solar energy devices, forms two oxides. One has \(28.8 \%\) O, by mass, and the other, 37.8\% O. What are the formulas of these oxides? Propose acceptable names for them.

Short Answer

Expert verified
The formulas are Selenium Dioxide (\(SeO_2\)) and Selenium Trioxide (\(SeO_3\)).

Step by step solution

01

Convert Percentage Composition to Masses

Assume a 100g sample of each compound. Hence, one compound will have \(28.8g\) of Oxygen and \(71.2g\) of Selenium (since \(100g - 28.8g = 71.2g\) of Selenium). The other compound will have \(37.8g\) of Oxygen and \(62.2g\) of Selenium (since \(100g - 37.8g = 62.2g\) of Selenium).
02

Convert to Moles

The molar mass of Oxygen (\(O\)) is \(16g/mol\) and Selenium (\(Se\)) is \(78.96 g/mol\). For the first oxide, the moles of \(O = \frac{28.8}{16} = 1.8 mol\) and moles of \(Se = \frac{71.2}{78.96} = 0.9 mol\). For the second oxide, the moles of \(O = \frac{37.8}{16} = 2.3625 mol\) and moles of \(Se = \frac{62.2}{78.96} = 0.7875 mol\).
03

Find Empirical Formula

The ratio of \(O:Se\) for the first compound is \(1.8:0.9 = 2:1\) so the empirical formula is \(SeO_2\). The ratio of \(O:Se\) for the second compound is \(2.3625:0.7875 = 3:1\) so the empirical formula is \(SeO_3\).
04

Determine the Names of Compounds

The compound with empirical formula \(SeO_2\) is known as Selenium Dioxide, and the one with empirical formula \(SeO_3\) is often referred to as Selenium Trioxide.

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Most popular questions from this chapter

The important natural sources of boron compounds are the minerals kernite, \(\mathrm{Na}_{2} \mathrm{B}_{4} \mathrm{O}_{7} \cdot 4 \mathrm{H}_{2} \mathrm{O}\) and borax, \(\mathrm{Na}_{2} \mathrm{B}_{4} \mathrm{O}_{7} \cdot 10 \mathrm{H}_{2} \mathrm{O} .\) How much additional mass of mineral must be processed per kilogram of boron obtained if the mineral is borax rather than kernite?

Determine the mass percent \(H\) in the hydrocarbon isooctane, \(\mathrm{C}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CH}_{2} \mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\)

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