Problems A
153
(e) An aluminum rod 20.0 cm long and 1.00 cm in diameter. The density of
aluminum is 2.70 g/ml.
5. In Friedrich Wohler's Grundriss der Chemie, published in 1823. the atomic
weight of oxygen is given as 100. On this basis calculate the molecular weight
of NH 4 Cl.
6. From the following analytical results (percentage by weight), determine the
empirical formulas for the compounds analyzed.
(a) 77.7% Fe, 22.3% O
(f) 92.4% C, 7.6% H
(b) 70.0% Fe, 30.0% O
(g) 75.0% C, 25.0% H
(c) 72.4% Fe, 27.6% O
(h) 21.8% Mg, 27.9%P, 50.3% O
(d) 40.2% K, 26.9% Cr, 32.9% O
(i) 66.8% Ag, 15.9% V, 17.3% O
(e) 26.6% K, 35.4% Cr, 38.0% O
(j)52.8% Sn, 12.4% Fe, 16.0% C,
18.8% N
7. Weighed samples of the following hydrates are heated to drive off the water,
and then the cooled residues are weighed. From the data given, find the
formulas of the hydrates.'
(a) 0.695 g of CuSO 4 -A H 2 O gave a residue of 0.445 g
(b) 0.573 g of Hg(NO 3 ) 2 -.vH 2 O gave a residue of 0.558 g
(c) 1.205 g of Pb(C 2 H,O 2 ) 2 -.vH 2 O gave a residue of 1.032 g
(d) 0.809 g of CoCl 2 -.vH 2 O gave a residue of 0.442 g
(e) 2.515 g of CaSO 4 -.vH 2 O gave a residue of 1.990g
8. Weighed samples of the following metals are completely converted to other
compounds by heating them in the presence of other elements, and then
are reweighed to find the increase in weight. The excess of the nonmetal is
easily removed in each case. From the data given, find the formulas of the
compounds formed.
(a) 0.527 g of Cu gave a 0.659 g residue with S
(b) 0.273 g of Mg gave a 0.378 g residue with N,
(c) 0.406 g of Li gave a 0.465 g residue with H 2
(d) 0.875 g of Al gave a 4.325 g residue with C1 2
(e) 0.219 g of La gave a 0.256 g residue with O 2
9. From a specific heat measurement, the approximate atomic weight of a metal
is found to be 136. A 0.3167 g sample of this metal is heated to constant weight
in air to convert it to the oxide, yielding a residue that weighs 0.3890 g. Find
the true atomic weight of the metal.
10. The following values of isotopic atomic weights and abundances are obtained
with a mass spectrometer. Compute the chemical atomic weights for the
elements involved. The isotopic weights are in parentheses.
(a) For neon: 90.51% (19.99872). 0.28% (20.99963). and 9.21% (21.99844).
(b) For sulfur: 95.06% (31.98085). 0.74% (32.98000), 4.18% (33.97710), and
0.02% (35.97800).
11. It is found experimentally that when a metal M is heated in chlorine gas, 0.540
g of M gives 2.67 g of metal chloride. The formula of the chloride is not
known.
153
(e) An aluminum rod 20.0 cm long and 1.00 cm in diameter. The density of
aluminum is 2.70 g/ml.
5. In Friedrich Wohler's Grundriss der Chemie, published in 1823. the atomic
weight of oxygen is given as 100. On this basis calculate the molecular weight
of NH 4 Cl.
6. From the following analytical results (percentage by weight), determine the
empirical formulas for the compounds analyzed.
(a) 77.7% Fe, 22.3% O
(f) 92.4% C, 7.6% H
(b) 70.0% Fe, 30.0% O
(g) 75.0% C, 25.0% H
(c) 72.4% Fe, 27.6% O
(h) 21.8% Mg, 27.9%P, 50.3% O
(d) 40.2% K, 26.9% Cr, 32.9% O
(i) 66.8% Ag, 15.9% V, 17.3% O
(e) 26.6% K, 35.4% Cr, 38.0% O
(j)52.8% Sn, 12.4% Fe, 16.0% C,
18.8% N
7. Weighed samples of the following hydrates are heated to drive off the water,
and then the cooled residues are weighed. From the data given, find the
formulas of the hydrates.'
(a) 0.695 g of CuSO 4 -A H 2 O gave a residue of 0.445 g
(b) 0.573 g of Hg(NO 3 ) 2 -.vH 2 O gave a residue of 0.558 g
(c) 1.205 g of Pb(C 2 H,O 2 ) 2 -.vH 2 O gave a residue of 1.032 g
(d) 0.809 g of CoCl 2 -.vH 2 O gave a residue of 0.442 g
(e) 2.515 g of CaSO 4 -.vH 2 O gave a residue of 1.990g
8. Weighed samples of the following metals are completely converted to other
compounds by heating them in the presence of other elements, and then
are reweighed to find the increase in weight. The excess of the nonmetal is
easily removed in each case. From the data given, find the formulas of the
compounds formed.
(a) 0.527 g of Cu gave a 0.659 g residue with S
(b) 0.273 g of Mg gave a 0.378 g residue with N,
(c) 0.406 g of Li gave a 0.465 g residue with H 2
(d) 0.875 g of Al gave a 4.325 g residue with C1 2
(e) 0.219 g of La gave a 0.256 g residue with O 2
9. From a specific heat measurement, the approximate atomic weight of a metal
is found to be 136. A 0.3167 g sample of this metal is heated to constant weight
in air to convert it to the oxide, yielding a residue that weighs 0.3890 g. Find
the true atomic weight of the metal.
10. The following values of isotopic atomic weights and abundances are obtained
with a mass spectrometer. Compute the chemical atomic weights for the
elements involved. The isotopic weights are in parentheses.
(a) For neon: 90.51% (19.99872). 0.28% (20.99963). and 9.21% (21.99844).
(b) For sulfur: 95.06% (31.98085). 0.74% (32.98000), 4.18% (33.97710), and
0.02% (35.97800).
11. It is found experimentally that when a metal M is heated in chlorine gas, 0.540
g of M gives 2.67 g of metal chloride. The formula of the chloride is not
known.