Chapter 19 Test Flashcards
Which of the following is the properly balanced equation for the net ionic equation below in acidic solution?
MnO4-(aq) + CN-(aq) -> MnO2(aq) + OCN-(aq)
2H+(aq) + 2MnO4-(aq) + 3CN-(aq) -> 2MnO2(aq) + H2O(l) + 3OCN-(aq)
What is the oxidation state of the chromium atom in each of the compounds listed below?
Na2Cr2O7, CrO2, and Cr3+
+6, +4, and +3
In the reaction of sodium chlorate and iron(II) sulfate below, which of the following represents the reduction half reaction?
NaClO3(aq) + 8FeSO4(aq) + 4HSO4-(aq) -> NaClO(aq) + 4Fe2(SO4)3(aq) + 2H2O(l)
4e- + ClO3-(aq) -> ClO-(aq)
Manganese can be found in many oxidation states. Which of the following is the strongest oxidant?
MnO4−, MnO2, MnCl2, Mn
MnO4−
In the diagram of a galvanic cell, which is the cathode?
D
Use the standard reduction potentials to calculate the E°cell for the following reaction in an electrolytic cell
Cu2+(aq) + 2Ag(s) -> Cu(s) + 2Ag+(aq)
−0.46 V
Calculate the standard Gibbs free energy change in J / mol at 25°C for the following reaction:
Zn2+(aq) + Cu(s) -> Zn(s) + Cu2+(aq)
Based on this ΔG ̊, would you expect Zn2+ ions to plate out on Cu metal?
2.123 * 10^5 J/mol, no
Calculate the Ecell for the Cl2/Cl- electrode for 25°C, given these values:
PCl2 = 12.0 atm [Cl-] = 1.25*10^-3M Cl2(g) = 2e- -> 2Cl-(aq) E° = +1.36V
+1.56 V
Which equation best describes the solubility of AgCl?
Ksp = e^(nFE°cell/RT)
Which of the following has the highest energy-to-mass ratio?
lithium battery
The transfer of electrons from iron to oxygen and water is all that is necessary for the formation of rust.
false
Given the following standard reduction potentials, which of the following would not be a good choice as a sacrificial anode for iron?
nickel
How many milligrams of copper metal would be produced in 24 hours of electroplating of a copper(II) ion solution with 9.0 A of current?
Faraday’s constant is 96,485 coulombs per mole of electrons
1 A = 1 C/s
260,000 mg Cu
A strip of copper is placed in a beaker with a 1.0 M solution of Cu(NO3 )2. A strip of silver is placed in a second beaker with A 1.0 M solution of AgNO3. A salt bridge connects the two beakers and the two metal electrodes are connected by wires to a digital voltmeter. The voltmeter reads 0.46 V. Which reaction is occurring at the anode and which reaction is occurring at the cathode? Note: In this cell, the standard reduction potential for Ag | Ag+ is + 0.80 V and the standard reduction potential for Cu | Cu2+ is + 0.34 V.
Anode Reaction: Cu -> Cu2+ + 2e-
Cathode Reaction: Ag+ + e- -> Ag
What is the chemical formula for rust?
Fe2O3 • H2O
Where does reduction occur in an electrolytic cell?
Cathode
Why is zinc used in batteries?
It is a good reducing agent
What is a volt?
joule per coulomb
What is reduction in a redox reaction?
A gain of electrons
What is the pH of a solution used in the following galvanic cell with a potential (Ecell ) of −0.365 V at 25°C?
Ni(s)|Ni2+ (0.1M)||H + (?)|H2(1 atm)
R • T / F = 0.0592 at 25°C
10.5
Which of the following is a disadvantage of a lead-acid storage battery?
it has a low energy-to-mass ratio
Mercury dry cell batteries are very stable because all of the phases comprising it are either solid or liquid. Why isn’t the mercury battery more commonly used?
Mercury is a toxic heavy metal and it is not used more often because of the environmental issues.
Why must the switch be open to measure EMF?
Because of resistance in the cell
What is the balanced equation representing the decomposition of hydrogen peroxide in acidic conditions?
H2O2(aq) –> H2(g) + O2(g)
2H+(aq) + 2H2O2(aq) -> H2(g) + O2(g) + 2H2O(l)
The state capitol of Iowa has a gold dome. The mass of gold used in plating the dome is 100 troy ounces (1.00 troy ounce = 31.10 grams). How many days would it take to plate out this quantity of gold from an 1.0 M aqueous solution of AuCl3 using an external current of 7.5 A?
7
