Honors Chemistry
Name___________________________
Chapter 6 Challenge/Review Problems
Directions:
Work out the following problems. Your work should be neat,
organized, and correct. You must show your work to get credit.
Make sure to put a box around your final answers. If you want to
make sure your answers match those at the end of this
assignment, use 6.02 X 1023 for Avogadro’s number. This
assignment is due Tuesday, November 24th (the day of the test).
1) How many gold atoms are in 5.0 cm3 of gold? The density of gold is 19.3 g/cm3.
2) Suppose you have a noble gas and find that 0.800 grams contains 1.204 X 1023 atoms
of the gas. What is the molar mass and identity of the gas?
3) How many grams of carbon dioxide are in 9.03 X 1024 molecules of carbon dioxide
gas?
4) How many grams of silver nitrate (AgNO3) are in 3.5 moles of silver nitrate?
5) A 2.0-L bottle of soda is made of mostly water. About how many water molecules are
in a 2.0-L bottle of soda, assuming it is all water? Assume the density of water is 1.0
g/mL.
6) If the same 2.0-L soda bottle is filled with carbon dioxide gas (density = 1.965 X 10-3
g/mL), how many CO2 molecules will be present in that container?
7) What is the mass of 3.25 X 10-4 mol of sulfur hexafluoride?
8) What is the mass, in grams, of 5 carbon monoxide molecules?
9) How many carbon atoms are in 12.5 g of sugar? (Sugar has the formula C12H22O11;
1 g = 1 X 10-6 g.)
10) The weight of a diamond is given in carats, where 1 carat = 200 milligrams (exact).
A pure diamond is made entirely of carbon atoms. How many carbon atoms are in a
2.00 carat diamond?
11) How many grams of oxygen is contained in 75 g of sulfur dioxide, SO2?
12) The density of gases can be measured in grams/liter. At room temperature, the
density of oxygen gas is 1.30 g/L. How many moles of oxygen gas can be found in
1.00 ft3 of oxygen gas at room temperature? 1 ft = 12 in, 1 in = 2.54 cm, 1 L = 1000
mL, 1 mL = 1 cm3
13) What is the percent silver (by mass) in silver phosphate?
14) How many grams of potassium can be obtained from 1.780 g of potassium
hydrogen phosphate?
15) The element iodine forms a compound with an alkaline earth metal (a Group II
metal). The compound is found to be 74.34 % iodine by mass. What is the molar
mass and identity of the Group II metal?
16) A certain compound is found to contain 65.2% arsenic and 34.8% oxygen by mass.
The molar mass of the compound is 460. grams. What is the empirical formula and
molecular formula of the compound?
17) The hormone epinephrine is released by the human body during stress. Like many
biological compounds, it is composed of carbon, hydrogen, oxygen, and nitrogen.
The percent composition of this hormone is 56.8% C, 6.56% H, 28.4% O, and 8.28%
N. What is the empirical formula for epinephrine?
18) A 20.882-gram sample containing just sodium, sulfur and oxygen is found to contain
6.072 grams of Na, 8.474 grams of S, and 6.336 grams of O. What is the empirical
formula for this compound?
19) A 2.78 g sample of a compound containing nitrogen and oxygen is found to contain
1.02 g of nitrogen. What is the empirical formula of the compound?
20) A certain compound was found to be 92.24% C and 7.76% H. It was found that 1.00
grams of this compound contained 7.70 X 1021 molecules. What is the molecular
formula of the compound?
21) Hydrocarbons are organic compounds composed entirely of carbon and hydrogen.
When burned in oxygen, the products are carbon dioxide and water:
hydrocarbon + oxygen  carbon dioxide + water
A 0.1648 gram sample of a hydrocarbon was burned in the presence of oxygen,
producing 0.5171 g of carbon dioxide and 0.2114 g of water. What is the empirical
formula of the hydrocarbon?
22) A hydrocarbon is a compound that contains just carbon and hydrogen. In one
experiment, a 1.800 gram sample of a hydrocarbon is burned in oxygen, producing
5.857 grams of carbon dioxide and an unknown amount of water. It is found that
2.00 grams of the compound contains 1.23 X 10-2 mol of the compound. Determine
the empirical formula, molar mass, and molecular formula of the compound.
23) Iron (III)chloride exists as a hydrated crystal with the formula FeCl3  nH2O where n
is an integer. A student conducts an experiment to determine the value for n. She
takes 67.5 grams of the hydrated crystal and heats it for a long time. When she reweighs the anhydrous crystal, it weighs 46.7 grams. What is the value for n?
24) In an experiment to study the reaction of tungsten with chlorine, 1.000 g of tungsten
metal is combined with excess chlorine gas. When the reaction was complete, 2.157
grams of tungsten chloride was produced. Determine the formula for the tungsten
chloride produced in this experiment.
25) Magnesium sulfate exists as a hydrated crystal with the formula MgSO4  nH2O
where n is an integer. A student conducts an experiment to determine the value for
n. She determines the mass of a test tube and adds some hydrated crystal. She then
records the mass of the hydrated crystal plus the test tube. She then heats the test
tube for a long time, driving off all of the water. She then re-weighs the test tube.
Her data is given below. Using her data, calculate the value of n for the hydrated
crystal.
Mass of Test Tube
Mass of Test Tube + MgSO4  nH2O
Mass of Test Tube + MgSO4
18.362 grams
24.362 grams
21.292 grams
26) Acetylene is an excellent fuel often used in welder’s torches, and is made of just
carbon and hydrogen. Suppose 5.000 grams of acetylene is burned, yielding 16.90
g of carbon dioxide. It is known that 1 molecule of acetylene has a mass of
4.32 X 10-23 grams. The unbalanced reaction is given below.
Acetylene + O2 → CO2 + H2O
(a)
(b)
(c)
(d)
Calculate the empirical formula of acetylene.
Calculate the grams of water produced.
Calculate the molar mass of acetylene
Determine the molecular formula of acetylene
Answers:
1) 2.9 X 1023 atoms
4) 590 g
7) 0.0475 g
10) 2.00 X 1022 atoms
13) 77.311%
16) As2O5, As4O10
19) N2O3
22) C2H3, 163 g, C12H18
25) n = 7.001 ≈ 7
2) 4.00 g/mol, He
3) 660. g
5) 6.7 X 1025 molecules
6) 5.4 X 1022 molecules
8) 2.33 X 10-22 g
9) 2.64 X 1017 atoms
11) 37 g
12) 1.15 mol
14) 0.7992 g
15) 87.6 g, Sr
17) C8H11O3N
18) Na2S2O3
20) C6H6
21) CH2
23) n = 4.01 ≈ 4
24) WCl6
26) CH, 3.46 g H2O, 26.0 g/mol, C2H2