Empirical formulas Transitional Reasoning Practice

Questions

1. 1.

   A materials chemist synthesizes a binary sulfide by heating a 0.54 g sample of pure aluminum foil in an enclosed tube containing sulfur vapor until the metal is completely consumed. The reaction yields 1.50 g of a single, pure sulfide compound as the only product. Given that the molar mass of aluminum is 27.0 g/mol and the molar mass of sulfur is 32.0 g/mol, what is the empirical formula of this compound?

   • A) $\text{Al}_2\text{S}_3$
   • B) $\text{AlS}$
   • C) $\text{AlS}_2$
   • D) $\text{Al}_3\text{S}_2$
2. 2.

   A materials chemist analyzes a 4.64 g sample of an unknown solid silver oxide by heating it strongly until it completely decomposes into metallic silver and oxygen gas. The released oxygen gas is collected and found to occupy a volume of 224 mL at standard temperature and pressure (STP). Given that the molar mass of silver is 108.0 g/mol, the molar mass of oxygen is 16.0 g/mol, and the molar volume of an ideal gas at STP is 22.4 L/mol, what is the empirical formula of this oxide?

   • A) $\text{Ag}_4\text{O}$
   • B) $\text{AgO}$
   • C) $\text{Ag}_2\text{O}$
   • D) $\text{AgO}_2$
3. 3.

   An environmental chemist analyzing air samples near an industrial cooling facility isolates a volatile chlorofluorocarbon (CFC) refrigerant. Quantitative elemental analysis determines that the pure compound contains 9.9% carbon, 58.7% chlorine, and 31.4% fluorine by mass. Given the molar masses of $\text{C} = 12.0\text{ g/mol}$, $\text{F} = 19.0\text{ g/mol}$, and $\text{Cl} = 35.5\text{ g/mol}$, what is the empirical formula of this compound?

   • A) $\text{CCl}_2\text{F}_2$
   • B) $\text{CCl}_3\text{F}$
   • C) $\text{C}_2\text{Cl}_2\text{F}_3$
   • D) $\text{CClF}_2$
4. 4.

   In a laboratory experiment, a student completely reacts a 3.36 g sample of pure iron powder with excess oxygen gas in a closed crucible, producing 4.80 g of a reddish-brown iron oxide as the sole product. Given the molar masses of iron ($\text{Fe} = 56.0\text{ g/mol}$) and oxygen ($\text{O} = 16.0\text{ g/mol}$), which of the following is the empirical formula of this compound?

   • A) $\text{FeO}$
   • B) $\text{Fe}_2\text{O}_3$
   • C) $\text{Fe}_3\text{O}_4$
   • D) $\text{FeO}_2$
5. 5.

   An analytical chemist investigates an unknown chlorinated hydrocarbon to determine its empirical formula. Complete combustion of a 4.95 g sample yields 4.40 g of carbon dioxide ($\text{CO}_2$) and 1.80 g of water ($\text{H}_2\text{O}$), with all remaining mass confirmed to be chlorine. Given the molar masses of $\text{C} = 12.0\text{ g/mol}$, $\text{H} = 1.0\text{ g/mol}$, $\text{O} = 16.0\text{ g/mol}$, and $\text{Cl} = 35.5\text{ g/mol}$, what is the empirical formula of the compound?

   • A) $\text{CHCl}$
   • B) $\text{C}_2\text{H}_4\text{Cl}$
   • C) $\text{CH}_2\text{Cl}$
   • D) $\text{CHCl}_2$

Answers and step-by-step solutions appear after you finish the test.