Download Extra Credit-Stoichiometry-2009

Extra Credit-Quarter Test
4 points for each problem
Question 5 must be answered correctly or no credit for anything!!
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1. A compound of formula XCl3 reacts with aqueous AgNO3 to yield a
precipitate of solid AgCl. When a solution containing 0.634 g of XCl3
was allowed to react with an excess of aqueous AgNO3, 1.68 g of
solid AgCl was formed. What is the identity of element X?
2. 70 grams of a mixture of silver nitrate and calcium nitrate solids are
dissolved in water. Hydrochloric acid is added to the solution. A
silver chloride precipitate forms which has a mass of 28.66 grams. If
10.95 grams of hydrochloric acid was added, what is the mass% of
silver nitrate in the mixture?
3. A petroleum chemist isolated a component of gasoline and found its
molar mass to be 114g/mol. When a 1.55 g sample of this compound
is burned in excess oxygen, 2.21 g of H2O and 4.8 g of CO2 are
formed. Find the empirical and molecular formulas.
4. Nitric acid, a leading industrial chemical, is used in the production of
fertilizers and explosives. One step in the industrial production of
nitric acid is the reaction of ammonia with molecular oxygen to form
nitrogen oxide and water. In a study of this reaction, a chemist mixed
125 g of ammonia with 256 g of oxygen and allowed them to react to
completion. What masses of NO and H2O were produced, and what
mass of what reactant was left over.
5- Douglasite is a mineral with the formula 2KCl●FeCl2 ● 2H2O Calculate
the mass percent of douglasite in a 455.0 mg sample if it took 37.20 ml
of a 0.100 M AgNO3 to precipitate all of the chloride. The douglasite is
the only source of chloride.