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Unformatted text preview: ter. The density of the solution
is 1.12 g/ml. What is the molarity of the solution? A) 1.5 M; B) 1.38 M; C) 1.24 M; D) 1.11 M; E) 213 g/litre
Molarity is the number of moles of solute per the volume of solution in liters. 42.6 g of Na2SO4
42.6
make
= 0.300 moles (3 significant figures). The volume of the solution is
142.05
42.6 g + 200 g
0.300
= 217 ml = 0.217 l (3 significant figures). The molarity is
= 1.38 M
1.12 g/ml
0.217
(3 significant figures).
12. 11.2 g of potassium hydroxide KOH were dissolved in water in a volumetric flask so that the
total volume of the solution obtained was 200 ml. The density of the solution was 1.20 g/ml.
What is the molarity of the solution? A) 1.00 M; B) 1.14 M; C) 1.2 M; D) 1.47 M; E) 56.0 g/litre
In this situation, the volume of the solution is known since the solution was prepared in the
volumetric flask and the necessary amount of water was added to obtain 200 ml of the solution.
11.2 g
Therefore, the density of solution is not needed. We simply have
= 0.200 moles of
56.11g / mol
0.200mol
KOH (3 significant figures), which gives
= 1.00 M solution of KOH.
0.200l
13. Consider the following reaction: BaCl2 (aq) + K2SO4 (aq) → BaSO4 (s) + 2 KCl (aq)
What are the spectator ions in this reaction?
A) K+ and Cl; B) Ba2+ and SO42; C) none; D) K+; E) Ba2+, K+, Cl and SO42.
To answer the question, we need to write the total ionic equation and indicate which ions are
found both on the left and on the right sides of it.
The total ionic equation is:
Ba2+ (aq) + 2 Cl (aq) + 2 K+ (aq) + SO42 (aq) → BaSO4 (s) + 2 K+ (aq) + 2 Cl (aq).
The spectator ions are K+ and Cl. Chemistry 1024b, Winter 2009 Midterm Exam with Solutions Page 4 out of 9 14. Consider the following reaction: BaCl2 (aq) + Ag2SO4 (aq) → BaSO4 (s) + 2 AgCl (s)
What are the spectator ions in this reaction?
A) K+ and Cl; B) Ag2+ and SO42; C) none; D) K+; E) Ag2+, K+, Cl and SO42.
To answer the question, we need to write the total ionic equation and indicate which ions are
found both on the left and on the right sides o...
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 Winter '12
 Dr.ZhifengDing
 Chemistry

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