CHEM 102. Worksheet 6: Stoichiometry and Solutions
Dr. Gunasekera
1. How many grams of magnesium sulfate should be added to 425 mL of de-ionized water to make a 0.075 M
solution?
2. A solution containing 320.4 g of Mg(NO3)2 per liter has a density of 1.114 g/mL. The molarity of the solution is:
3. The term "proof" is defined as twice the percent by volume of pure ethanol in solution. Thus, a solution that is
95% (by volume) ethanol is 190 proof. What is the molarity of ethanol in a 92 proof ethanol/water solution?
density of ethanol
= 0.80 g/cm3
density of water
= 1.0 g/cm3
mol. wt. of ethanol = 46 g/mol
4. The specific gravity of antifreeze (ethylene glycol: C2H6O2) 1.09. What is the mass (in kilograms) of antifreeze
that is needed to make 12000L of 7.50% (v/v) mixture to be used to melt ice in an airport?
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CHEM 102. Worksheet 6: Stoichiometry and Solutions
Dr. Gunasekera
5. An impure sample of lime weighing 0.150g was reacted with 50.00cm3 of 0.8mol/L hydrochloric acid. After the
reaction was complete the solution was transferred to a 250cm3 volumetric flask and made up to the mark with
distilled water. A 25.00cm3 portion of this solution was then titrated against 0.25mol/L sodium hydroxide
using methyl orange as the indicator. A 15.00cm3 volume of the sodium hydroxide was consumed. Calculate the
percentage purity of lime sample. Unbalanced equations are as follows;
CaCO3(s) + HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)
6. From the balanced molecular equations, write the complete ionic and net ionic equations for the following:
a. K2C2O4(aq) + Ba(OH)2(aq) → 2KOH(aq) + BaC2O4(s)
b. Pb(NO3)2(aq) + H2SO4(aq) → PbSO4(s) + 2HNO3(aq)
c. CaCO3(s) + H2SO4(aq) → CaSO4(s) + CO2(g) + H2O(l)
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CHEM 102. Worksheet 6: Stoichiometry and Solutions
Dr. Gunasekera
7. Determine the oxidation states of the elements in the compounds listed. None of the oxygen-containing
compounds are peroxides or superoxides.
d.
e.
f.
g.
h.
i.
H3PO4
Al(OH)3
SeO2
KNO2
In2S3
P4O6
8. What volume of a 0.2089 M KI solution contains enough KI to react exactly with the Cu(NO3)2 in 43.88 mL of a
0.3842 M solution of Cu(NO3)2?
2Cu ( NO3 )2 + 4KI ⎯⎯
→ 2CuI + I 2 + 4KNO3
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CHEM 102. Worksheet 6: Stoichiometry and Solutions
Dr. Gunasekera
9. Outline the steps needed to solve the following problem, then do the calculations. Ether, (C2H5)2O, which was
originally used as an anesthetic but has been replaced by safer and more effective medications, is prepared by
the reaction of ethanol with sulfuric acid.
2C2 H5OH + H 2SO4 ⎯⎯
→ ( C2 H5 )2 O + H 2SO4 gH2 O
What is the percent yield of ether if 1.17 L (d = 0.7134 g/mL) is isolated from the reaction of 1.500 L of C2H5OH
(d = 0.7894 g/mL)?
10. In a common medical laboratory determination of the concentration of free chloride ion in blood serum, a
serum sample is titrated with a Hg(NO3)2 solution.
2Cl – (aq) + Hg(NO3)2 (aq) ⎯⎯
→ 2NO3 – (aq) + HgCl2 ( s)
What is the Cl– concentration in a 0.25-mL sample of normal serum that requires 1.46 mL of 5.25
Hg(NO3)2(aq) to reach the end point?
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 10–4M