Chemistry 101. ANSWER KEY. 1. REVIEW QUESTIONS. Chapter 4. 1. Identify ...
7. How many mL of 1.50 M Na 3 PO 4 solution contains 5.00 g of solute? 5.00 g.
Chemistry 101
ANSWER KEY REVIEW QUESTIONS Chapter 4
1. Identify each of the following substances as a non-electrolyte (NE), weak electrolyte (WE), or strong electrolyte (SE): a)
HF
WE
b)
C2H5OH
NE
c)
LiOH
SE
d)
HClO3
SE
e)
Cu(NO3)2
f)
H3PO4
WE
SE
2. Complete each equation shown below:
a)
H 2 O AlCl3 (s) ¾¾¾ ® Al3+ (aq) + 3 Cl – (aq)
b)
H 2 O Na3PO4 (s) ¾¾¾ ® 3 Na+ (aq) + PO43– (aq)
c)
H 2 O (NH4)2CO3 (s) ¾¾¾ ® 2 NH4+ (aq) + CO32– (aq)
3. Complete the molecular equations shown below, and write balanced net ionic equations for each:
5. Write balanced net ionic equations for each reaction described below: a) Solid sodium hydroxide pellets are dropped in solution of sulfuric acid. 2 NaOH (s) + H2SO4 (aq) ® Na2SO4 (aq) + 2 H2O (l) NaOH (s) + H+ (aq) ® Na+ (aq) + H2O (l) b) Aqueous solutions of ammonium carbonate and calcium chloride are mixed together. (NH4)2CO3 (aq) + CaCl2 (aq) ® CaCO3 (s) + 2 NH4Cl (aq) CO32– + Ca2+ ® CaCO3 (s)
2
6. How many grams of solute are present in 50.0 mL of 1.33 M CuSO4 solution? 50.0 mL x
1.33 mol CuSO 4 159.55 g x = 10.6 g CuSO 4 1000 mL 1 mol
7. How many mL of 1.50 M Na3PO4 solution contains 5.00 g of solute? 1 mol 1000 mL 5.00 g x x = 20.3 mL 164.0 g 1.50 mol
8. What volume of 1.50 M solution of sucrose solution is required to prepare 425 mL of 0.100 M solution? V2 =
M 1 V 1 (0.100 M )(425 mL) = = 28.3 mL M 2 1.50 M
9. Glacial acetic acid has a density of 1.049 g/mL at 25°C. What is the molarity of a solution of acetic acid prepared by dissolving 10.00 mL of glacial acetic acid at 25°C in enough water to make 100.0 mL of solution? 10.00 mL x
1.049 g 1 mol 1 x x =1.747 M 1 mL 60.04 g 0.1000 L
10. How many mL of 2.15 M KOH are required to titrate 25.0 mL of 0.300 M HC2H3O2? HC2H3O2 + KOH ® KC2H3O2 + H2O 25.0 mL HC2 H 3O 2 x
0.300 mol 1 mol KOH 1000 mL x x = 3.49 mL KOH 1000 mL 1 mol HC2 H 3O 2 2.15 mol
3
11. Determine the concentration of a Ba(OH)2 solution, if 15.0 mL of the base are required to titrate 25.0 mL of 0.525 M HNO3 to an end point. 2 HNO3 + Ba(OH)2 ® Ba(NO3)2 + 2 H2O 25.0 mL HNO 3 x
0.525 mol 1 mol Ba(OH) 2 1 x x = 0.438 M 1000 mL 2 mol HNO 3 0.0150 L
12. A 28.7 mL sample of 1.02 M HCl is required to neutralize the NH3 present in a 5.00 mL sample of window cleaner solution. What is the molarity of NH3 in this solution? HCl + NH3 ® NH4Cl 28.7 mL HCl x
1.02 mol 1 mol NH 3 1 x x = 5.85 M 1000 mL 1 mol HCl 5.00x10 3 L
13. The acetylsalicylic content of aspirin can be determined by titration of the acid with base as shown below: HC9H7O4 + acetylsalicylic acid
NaOH ®
NaC9H7O4
+
H2O
23.0 mL of 0.0770 M NaOH solution was used to neutralize the acid in a 500-mg aspirin tablet. What is the percent of acetylsalicylic acid in the aspirin tablet? HC9H7O4 + NaOH ® NaC9H7O4 + H2O 23.0 mL NaOH x
0.0770 mol 1 mol HC9 H 7 O 4 180.1 g 103 mg x x x = 319 mg HC9 H 7 O 4 1000 mL 1 mol NaOH 1 mol 1 g
% Acid =
319 mg x100 = 63.8% 500 mg
4
14. In the compounds below, assign oxidation numbers to the underlined element: a)
H3PO2
P : +1
d) H2CO
C:
0
b)
Na2C2O4
C : +3
e) ClF4–
Cl :
+3
c)
MnSO4
S:
g) AlH3
H:
–1
+6
15. Identify which substance is oxidized and which substance is reduced in each of the following redox reactions. 0
a)
0
+3 –1
2 Al + 3 Cl2 ® 2 AlCl3 oxidized –2
b)
0
Al
reduced
Cl
S
reduced
O
reduced
N
–2 +4
2 NiS + 3 O2 ® 2 NiO + 2 SO2 oxidized –2 +5 0 +2
c) 3 H2S + 2 HNO3 ® 3 S + 2 NO + 4 H2O Oxidized
S
16. For each reaction shown below, write oxidation and reduction half-reactions. a)
Fe (s) + Cu2+ (aq) ® Cu (s) + Fe2+ (aq) Oxidation half-reaction:
Fe (s) ® Fe2+ (aq) + 2 e–
Reduction half-reaction:
Cu2+ (aq) + 2 e– ® Cu (s)
b) Mg (s) + 2 HCl (aq) ® MgCl2 (aq) + H2 (g) Oxidation half-reaction:
