Chem 1711
Name _______________________________________
Quiz 4 (25 points)
October 9, 2013
[H+][OH—] = 1 x 10—14
1.
2.
pH = —log[H+]
Indicate whether each of the following statements are true or false:
a.
An aqueous solution prepared by dissolving Na2O (s) in water will turn blue litmus paper red.
_________________
b.
The oxidation number of chlorine in Cl2O7 is —1.
_________________
c.
A solution with a pH greater than 7 will have [H+] < [OH—].
_________________
d.
The pH of 0.25 M Ca(OH)2 (aq) will be equal to the pH of 0.50 M LiOH (aq).
_________________
Use the half-reaction method to balance the following redox reaction that occurs in acidic solution:
MnO4— + SO2  Mn2+ + SO42—
Oxidation half-reaction:
Reduction half-reaction:
Net reaction:
3.
4.
Consider the reaction: K2Cr2O7 (aq) + 6 FeCl2 (aq) + 14 HCl (aq)  2 CrCl3 (aq) + 6 FeCl3 (aq) + 2 KCl (aq) + 7 H2O (l)
a.
During the course of this reaction the oxidation number of Fe changes from __________ to __________ .
b.
In this reaction K2Cr2O7 is {the oxidizing agent, the reducing agent, neutralized, or precipitated}.________________
c.
21.46 mL of FeCl2 (aq) are required to reach the stoichiometric point in the titration of 40.00 mL of 0.267 M K2Cr2O7
(aq). Calculate the molar concentration of FeCl2 (aq).
Aqueous solutions of hydrofluoric acid and potassium hydroxide are combined and allowed to react. Which one of the
following is the net ionic equation for this reaction? Circle the one best answer.
a.
H+ (aq) + OH— (aq)  H2O(l)
c.
HF (aq) + KOH (aq)  K+ (aq) + F— (aq) + H2O (l)
b.
HF (aq) + OH— (aq)  F— (aq) + H2O (l)
d.
H+ (aq) + F— (aq) + K+ (aq) + OH—  KF (aq) + H2O (aq)
5.
Calculate the pH of 0.00643 M HBr (aq).
pH = _____________________
6.
Using the Activity Series of Metals and your knowledge of the relative reactivity of halogens, determine which one of the
following reactions will not occur as written. Circle the one best answer below.
a. 2 Co (s) + 6 HNO3 (aq)  2 Co(NO3)3 (aq) + 3 H2 (g)
c. Cl2 (g) + 2 NaI (aq)  2 NaCl (aq) + I2 (s)
b. Sn (s) + ZnCl2 (aq)  SnCl2 (aq) + Zn (s)
d. 2 Na (s) + 2 H2O (l)  2 NaOH (aq) + H2 (g)
7.
Write the balanced chemical equation to describe the reaction that will occur when aqueous solutions of perchloric acid
and cesium hydroxide are combined. Include all physical states.
8.
Matching. Match the description on the left with the one best term on the right.
9.
a.
reactant that facilitates oxidation
_______
i. oxidation
v. reducing agent
b.
reaction that occurs when an HBr is added to CaCO3
_______
ii. reduction
vi. oxidizing agent
c.
change that occurs when Cl2 (g) reacts to form Cl—
_______
iii. precipitation
vii. base
d.
proton acceptor
_______
iv. neutralization
viii. acid
A 32.305 g sample of a soluble phosphate salt is dissolved in water. Excess Mg(NO3)2 (aq) is added to this solution, and
a precipitate of Mg3(PO4)2 is formed. 12.086 g Mg3(PO4)2 is collected. Determine the mass percent phosphate in the
original sample. For Mg3(PO4)2, molar mass = 262.9 g/mol.
Chem 1711
Name _______________________________________
Quiz 4 (25 points)
October 9, 2013
[H+][OH—] = 1 x 10—14
1.
2.
pH = —log[H+]
Matching. Match the description on the left with the one best term on the right.
a.
reactant that facilitates reduction
_______
i. oxidation
v. reducing agent
b.
change that occurs when Cl— reacts to form Cl2
_______
ii. reduction
vi. oxidizing agent
c.
proton donor
_______
iii. precipitation
vii. base
d.
reaction that occurs when an HBr is added to CaCO3
_______
iv. neutralization
viii. acid
Using the Activity Series of Metals and your knowledge of the relative reactivity of halogens, determine which one of the
following reactions will not occur as written. Circle the one best answer below.
a. 2 Co (s) + 6 HNO3 (aq)  2 Co(NO3)3 (aq) + 3 H2 (g)
c. Sn (s) + ZnCl2 (aq)  SnCl2 (aq) + Zn (s)
b. Cl2 (g) + 2 NaI (aq)  2 NaCl (aq) + I2 (s)
d. 2 Na (s) + 2 H2O (l)  2 NaOH (aq) + H2 (g)
3.
Write the balanced chemical equation to describe the reaction that will occur when aqueous solutions of perchloric acid
and cesium hydroxide are combined. Include all physical states.
4.
A 32.305 g sample of a soluble phosphate salt is dissolved in water. Excess Mg(NO3)2 (aq) is added to this solution, and
a precipitate of Mg3(PO4)2 is formed. 12.086 g Mg3(PO4)2 is collected. Determine the mass percent phosphate in the
original sample. For Mg3(PO4)2, molar mass = 262.9 g/mol.
5.
Use the half-reaction method to balance the following redox reaction that occurs in acidic solution:
MnO4— + SO2  Mn2+ + SO42—
Oxidation half-reaction:
Reduction half-reaction:
Net reaction:
6.
Aqueous solutions of hydrofluoric acid and potassium hydroxide are combined and allowed to react. Which one of the
following is the net ionic equation for this reaction? Circle the one best answer.
a.
H+ (aq) + OH— (aq)  H2O(l)
c.
HF (aq) + KOH (aq)  K+ (aq) + F— (aq) + H2O (l)
b.
HF (aq) + OH— (aq)  F— (aq) + H2O (l)
d.
H+ (aq) + F— (aq) + K+ (aq) + OH—  KF (aq) + H2O (aq)
7.
Calculate the pH of 0.00463 M HBr (aq).
8.
Indicate whether each of the following statements are true or false:
9.
pH = _____________________
a.
A solution with a pH greater than 7 will have [H+] < [OH—].
_________________
b.
The pH of 0.25 M Ca(OH)2 (aq) will be equal to the pH of 0.50 M LiOH (aq).
_________________
c.
An aqueous solution prepared by dissolving Na2O (s) in water will turn blue litmus paper red.
_________________
d.
The oxidation number of chlorine in Cl2O7 is —1.
_________________
Consider the reaction: K2Cr2O7 (aq) + 6 FeCl2 (aq) + 14 HCl (aq)  2 CrCl3 (aq) + 6 FeCl3 (aq) + 2 KCl (aq) + 7 H2O (l)
a.
During the course of this reaction the oxidation number of Cr changes from __________ to __________ .
b.
In this reaction FeCl2 is {the oxidizing agent, the reducing agent, neutralized, or precipitated}.
c.
21.46 mL of FeCl2 (aq) are required to reach the stoichiometric point in the titration of 40.00 mL of 0.267 M K 2Cr2O7
(aq). Calculate the molar concentration of FeCl2 (aq).
________________