Exam 3: Stoichiometry: Mass, Formulas, and Reactions

Elemental analysis of the soot produced by a candle flame shows that it is 14.3% H and 85.7% C by mass. What is the empirical formula of this hydrocarbon?

Dialuminum hexachloride, Al₂Cl₆ (266.66 g/mol) is an inexpensive compound that is used in many industrial processes. It is made by treating scrap aluminum with chlorine gas. If a reaction is run with 270 g of aluminum and 710 grams of chlorine, the limiting reactant is __________, and the theoretical yield is __________ grams of Al₂Cl₆. 2Al(s) + 3Cl₂(g) $\rightarrow$ Al₂Cl₆(s)

Ozone (O₃) reacts with iodide (I^-) and water to form iodine (I₂), hydroxide (OH^-), and oxygen (O₂). Balance the following reaction equation and report the sum of the stoichiometric coefficients. O₃ + I^- + H₂O $\rightarrow$ I₂ + OH^- + O₂

How much CO₂ is produced by a car driven 20,000 mi in one year? Assume the following: • A car gets 20 mi/4.0 L of gasoline. • Gasoline has the chemical formula of octane: C₈H₁₈. • One liter of gasoline has a mass of 0.8 kg. • Gasoline is completely burned to carbon dioxide and water.

The empirical formula for buckminsterfullerene is C₁, and its molar mass is 720.6 g/mol. What is its molecular formula?

In a self-contained breathing apparatus, potassium superoxide, KO₂, reacts with carbon dioxide to form potassium carbonate and oxygen. Identify the limiting reactant and determine the amount of oxygen gas, in moles, that can be produced from 250 g of KO₂ and 450 g of CO₂. 4KO₂(s) + 2CO₂(g) $\rightarrow$ 2K₂CO₃(s) + 3O₂(g)

How many moles of ammonia are there in a 346 g sample of pure NH₃ (17.03 g/mol)?

A tiny speck (2.0 * 10^-4 g) of radioactive americium-241 (241.06 g/mol) is used in smoke detectors. How many atoms of americium-241 are there in one of these smoke detectors?

Copper sulfate is a blue solid that is used to control algae growth. Solutions of copper sulfate that come in contact with the surface of galvanized (zinc-plated) steel pails undergo the following reaction that forms copper metal on the zinc surface. How many grams of zinc would react with 454 g (1 lb) of copper sulfate (160 g/mol)? CuSO₄(aq) + Zn(s) $\rightarrow$ Cu(s) + ZnSO₄(aq)

The most abundant metal in Earth's crust is aluminum, found mostly in the form of clays. There are no economical routes for extracting aluminum from clay. However, bauxite ore, impure hydrated aluminum oxide, is found in hot humid regions, such as Australia, Guinea, and Brazil, and it can be purified and refined to make the metal. After the first purification step, hydrated aluminum oxide (Al₂O₃ . xH₂O) is obtained. When 100.0 g of this solid were heated, and the water driven off, 65.36 g of Al₂O₃ remained. How many water molecules (x in the molecular formula) were there in the hydrate?

A burner in a gas grill mixes 20 volumes of air for every one volume of propane (C₃H₈). For gases at a given temperature and pressure, the volume that the gas occupies is directly proportional to the number of moles of the gas. Air is 21% oxygen by volume. Is the mixture produced by this burner rich (excess propane), lean (excess oxygen), or just right (a stoichiometric mixture of propane and oxygen)?

Without doing any calculations, identify which of the following compounds has the largest percent sodium by mass and which has the smallest. Explain your logic. sodium oxide, Na₂O; sodium hydroxide, NaOH; sodium hydrogen carbonate, NaHCO₃, sodium carbonate, Na₂CO₃; sodium peroxide, Na₂O₂

Why is the term formula unit more appropriate for an ionic compound such as sodium chloride, NaCl, than the term molecular formula?

A particular manufacturer sells phosphoric acid capsules as a homeopathic remedy with a concentration specified as 23X. (23X means that when averaged over many capsules, the average mass of phosphoric acid in one capsule is 10^-23 times the mass of the capsule. The rest is a carbohydrate filler.) If each capsule has a mass of 35 mg, approximately how many capsules would you have to take to expect to ingest at least one molecule of H₃PO₄ (98.0 g/mol)?

One mole is defined as __________

Hydrogen peroxide (H₂O₂) decomposes catalytically in the presence of metal ions and enzymes called peroxidases. You may have noticed this reaction occurring if you use a drugstore solution of hydrogen peroxide as a mouthwash or antiseptic. If a 250 mL bottle of hydrogen peroxide solution containing 3.0% H₂O₂ (by mass) completely decomposes, how many liters of oxygen gas would it generate? Assume that 1 mol of gas occupies a volume of 22.4 L and that the density of the solution is 1.0 g/mL. The reaction is 2H₂O₂(aq) $\rightarrow$ 2H₂O(l) + O₂(g)

One form of asbestos called chrysotile is considered to be a human carcinogen. Mass analysis reveals that it has the empirical formula Mg₃Si₂H₄O₉. If the molar mass is 277 g/mol, which molecular formula is correct?

Hydrogen peroxide decomposes to produce water and oxygen. Which relationship regarding the quantities of reactants and products associated with this reaction is not correct? 2H₂O₂ $\rightarrow$ 2H₂O + O₂

Identify the set of stoichiometric coefficients that balances the reaction equation for the combustion of octane. C₈H₁₈ + O₂ $\rightarrow$ CO₂ + H₂O

The combustion of butane (C₄H₁₀) forms carbon dioxide and water. What is the stoichiometric coefficient for oxygen in the balanced equation when 1 mol of butane undergoes combustion?