(18) Additional Challenges
Exercises
Extra questions:
a. Which has the higher percentage of magnesium in it--magnesium oxide or magnesium
nitride?
b. When magnesium is burned in oxygen, magnesium oxide is formed. When magnesium is
burned in air, some magnesium nitride is formed along with magnesium oxide. Will this make
the product from burning in air weigh more or less than the product from burning in
oxygen?
c. Which compound has the heaviest molecules--sulfur hexafluoride or carbon
tetrachloride? Which of those compounds has the most atoms per molecule?
d. Would the weight of magnesium oxide formed by burning 1.23 g of magnesium in ozone
(O3) be any different than the weight of magnesium oxide formed by burning 1.23
g of magnesium in molecular oxygen (O2)?
e. Which would yield the larger amount of iron--44 kg of ferrous oxide or 38 kg of
ferric oxide?
Answers to Exercises
Extra questions:
a. Which has the higher percentage of magnesium in it--magnesium oxide or magnesium
nitride?
Magnesium oxide is 60.3% Mg and magnesium nitride is 72.2% Mg, so the percentage of
magnesium is higher in magnesium nitride.
b. When magnesium is burned in oxygen, magnesium oxide is formed. When magnesium is
burned in air, some magnesium nitride is formed along with magnesium oxide. Will this make
the product from burning in air weigh more or less than the product from burning in
oxygen?
From the previous question, the percentage of magnesium in magnesium nitride is higher
than in magnesium oxide, therefore the percentage of the other element in magnesium
nitride is less than in magnesium oxide, therefore the increase in mass will be less
in forming magnesium nitride than in forming magnesium oxide.
c. Which compound has the heaviest molecules--sulfur hexafluoride or carbon
tetrachloride? Which of those compounds has the most atoms per molecule?
SF6 has 7 atoms per molecule and a formula weight of 146.
CCl4 has 5 atoms per molecule and a formula weight of 154.
CCl4 has heavier molecules and SF6 has more atoms per
molecule.
d. Would the weight of magnesium oxide formed by burning 1.23 g of magnesium in ozone
(O3) be any different than the weight of magnesium oxide formed by burning 1.23
g of magnesium in molecular oxygen (O2)?
Because the same product is formed in each case and the same amount of magnesium is the
limiting reagent in each case, the weight of the product will be the same.
e. Which would yield the larger amount of iron--44 kg of ferrous oxide or 38 kg of
ferric oxide?
44 kg of FeO will yield 34 kg of Fe
38 kg of Fe2O3 will yield 27 kg of Fe
More iron can be obtained from 44kg of ferrous oxide.
Top of Page
Back to Course Homepage
E-mail instructor:
Eden Francis
Clackamas Community College
©1998, 1999 Clackamas Community College, Hal Bender
