Chemistry Reference
In-Depth Information
Solution
Per gram of nitrogen, the following mass of oxygen is present in each of the
two compounds:
In nitrogen dioxide
In dinitrogen trioxide
69.55 g O
30.45 g N
2.284 g O
1 g N
63.15 g O
36.85 g N
1.714 g O
1 g N
The ratio of grams of oxygen in nitrogen dioxide (per gram of nitrogen) to
grams of oxygen in dinitrogen trioxide (per gram of nitrogen) is
2.284 g O
1.714 g O
1.333
1.000
3.999
3.000
4
3
This ratio is, within limits of experimental error, equal to a small, whole-
number ratio.
Note that it is
not
the ratio of mass of nitrogen to mass of oxygen
that must be an integral ratio, according to the law of multiple propor-
tions, but the ratio of the mass of oxygen in one compound to the mass of
oxygen in the other compound (for the same mass of nitrogen in the two
compounds).
Practice Problem 3.3
The percent compositions of two oxides
of iron are 77.73% Fe and 22.27% O for one oxide and 69.94% Fe and
30.06% O for the other. Show that these compounds obey the law of multiple
proportions.
How did the chemists of 1800 explain
why
compounds obeyed the law
of definite proportions and the law of multiple proportions? They didn't.
A theory to explain these and many other phenomena was just about to be
proposed.
Snapshot Review
❒
The empirical laws governing the masses of reactants and products of
chemical reactions formed the basis for the theoretical development
of chemistry.
A. What is the total mass of the mercury and oxygen produced from the
decomposition of 25.0 g of HgO?
B. Barium and chlorine combine in a ratio of 137.3 g of barium to 70.90 g
of chlorine. What is the percent chlorine in (a) a 5.00-g sample of the
compound? (b) a 10.0-g sample of the compound?
C. One compound of iron and chlorine contains 1.269 g of chlorine for each
gram of iron. A second compound of these elements contains 1.907 g of
chlorine for each gram of iron. Calculate the mass of iron per gram of
chlorine in each compound, and show that the masses obey the law
of multiple proportions.
