Honors Chemistry
Christmas Credit
Directions:
Name___________________________
Work out the following problems. Your work should be neat,
organized, and correct. Please put a box around your final
answers and units. You may print out this paper, or do your work
on a separate sheet of paper. You must show your work to get
credit.
1) 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?
2) Hydrocarbons are organic compounds composed entirely of carbon and hydrogen.
How do hydrocarbons react when they undergo combustion? (Look back at your
reaction notes!)
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?
3) 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.
4) 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.
5) 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. You need to do this
mathematically, don’t look up the formula.
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
6) A compound has an empirical formula of C3H5X3. A 7.000g sample was determined
to be 0.04751 mol of the compound. What is element “X”?
7) You have a mixture that contains sodium chloride and sodium chlorate. You want to
determine the percent of sodium chlorate in the mixture. You heat an 8.762 g
sample of the mixture intensely in a crucible, causing the sodium chlorate to
decompose into sodium chloride and oxygen gas. The oxygen gas escapes from the
crucible. The sodium chloride in the original sample does not react. The mass of the
solid in the crucible after the reaction is 6.503 g (original NaCl plus NaCl produced
in the reaction. What was the % of sodium chlorate in the original mixture?