Name: ________________________
Hour: ____ Date: ___________
AP Chemistry: 3HW
Directions: Complete the following problems.
Find the formula weight and molar mass of:
1A. tin(IV) sulfate
1B. aluminum bromite
2A. Find the mass of each element present in a 0.5625 g sample of ammonium cyanide.
2B. Suppose that a biological molecule is 0.435% iron by mass and that each such molecule contains three iron
atoms. Find the compound’s molar mass.
3A. Cholesterol is 83.94% carbon, 11.92% hydrogen, and 4.15% oxygen by mass. Find cholesterol’s empirical
formula.
ANSWERS:
1A. f.w. = 310.9 amu; mm = 310.9 g
1B. f.w. = 362.7 amu; mm = 362.7 g
2A. 0.3580 g N, 0.1534 g C, 0.0511 g H
2B. 38,500 g
3A. C27H46O
3B. Codeine is 72.24% carbon, 7.02% hydrogen, 16.05% oxygen, and 4.68% nitrogen by mass. Find codeine’s
empirical formula.
4A. A sample of a compound is found to contain 23.03 g phosphorus, 5.22 g nitrogen, and 26.39 g chlorine. The
compound’s molar mass is 441 g. Find its molecular formula.
4B. Lactic acid is a ternary oxyacid that is 40.00% carbon and 6.67% hydrogen. If 0.377 moles of lactic acid
have a mass of 33.93 g, find the molecular formula of lactic acid.
Given the following laboratory data, find the formula of each hydrate.
5A.
mass of beaker = 57.84 g
mass of beaker and contents before heating = 64.53 g
mass of beaker and contents after heating = 61.48 g
molar mass of anhydrous salt = 85.9 g
ANSWERS:
3B. C18H21O3N
4A. P6N3Cl6
4B. C3H6O3
5A. MN . 4 H2O
5B.
mass of beaker = 74.22 g
mass of beaker and contents before heating = 96.43 g
mass of beaker and contents after heating = 86.28 g
chemical name of anhydrous salt = barium hydroxide
6A. What volume is occupied at STP by approximately one billion atoms of neon?
6B. How many carbon atoms are in a 1.5-carat diamond? (1 carat = 0.200 g)
7A. How many nitrogen atoms are in 18.8 g of barium nitride?
7B. How many oxygen atoms are in 7.25 g of calcium nitrate?
8A. When lighting a match on a matchbox, red phosphorus (P4) reacts with potassium chlorate to form
potassium chloride and tetraphosphorus decoxide. If 0.113 g of potassium chlorate reacts with excess
red phosphorus, what mass of tetraphosphorus decoxide will be produced?
8B. Ammonium thiocyanate (NH4SCN) and barium hydroxide octahydrate (Ba(OH)2.8 H2O) react to produce
barium thiocyanate, water, and ammonia (NH3). What mass of ammonium thiocyanate reacts
completely with 24.8 g of barium hydroxide octahydrate?
ANSWERS:
5B. Ba(OH)2 . 8 H2O
6A. 4 x 10–14 L
6B. 1.5 x 1022 at.
7A. 5.15 x 1022 at.
7B. 1.60 x 1023 at.
8A. 0.0785 g
8B. 12.0 g
9A. The peroxide ion is O22–. Barium peroxide and nitric acid react to produce hydrogen peroxide and barium
nitrate. What mass of hydrogen peroxide is produced when 1.46 g of barium peroxide react with
30.0 mL of nitric acid solution that contains 0.0754 g of the acid per mL?
9B. In the gaseous reaction between ammonia, oxygen gas, and methane, hydrogen cyanide and water are
produced. Ideally, what mass of each product is yielded if you start with 600. g of each reactant?
10A. If 25.0 g of carbon monoxide react with 8.50 g of ammonia and 10.0 g of hydrogen to produce water and
acetonitrile (CH3CN), what mass of each excess reactant is left over after the reaction is complete?
ANSWERS:
9A. 0.293 g
9B. 338 g hydrogen cyanide;
675 g water
10A. 0.91 g ammonia;
8.21 g hydrogen
10B. Silver nitrate and cobalt(II) chloride react in solution to produce two products, one of which is a silver
chloride precipitate. If 87.4 g of silver nitrate and 38.5 g of cobalt(II) chloride are put together in solution,
what mass of excess reactant remains after the reaction is complete?
11A. Bornite (Cu3FeS3) is an ore that, when reacted with oxygen, will yield iron(II) oxide, sulfur dioxide, and
copper. If the process has a 75.5% yield, how many metric tons of copper are produced from the
reaction between excess oxygen and 5.25 metric tons of bornite? (1 metric ton = 1000 kg)
11B. In the reaction between red phosphorus (P4) and fluorine, phosphorus trifluoride is produced. If the percent
yield is 82.6%, what mass of fluorine is needed to produce 152 g of phosphorus trifluoride?
ANSWERS:
10B. 5.1 g
11A. 2.20 metric tons
11B. 119 g