Electrons are charged particles. The amount of charge that passes per unit time is called
voltage, current, potential
answer
current
question
The driving force for the electrons (the reason they are flowing in the first place) is measured by
potential, current, charge
answer
potential
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Charge is measured in
joules (J), volts (V), coulombs (C), amperes (A)
answer
coulombs (C)
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Current is measured in
coulombs (C), volts (V), joules (J), amperes (A)
answer
amperes (A)
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Potential is measured in
coulombs (C), amperes (A), joules (J), volts (V)
answer
volts (V)
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Gallium is produced by the electrolysis of a solution made by dissolving gallium oxide in concentrated NaOH. Calculate the amount of Ga that can be deposited from a Ga(III) solution using a current of 0.800 A that flows for 40 minutes.
answer
We use the equation: m = (It/F)(M/n)
Ga3+ + 3e- = Ga, thus n = 3
m = (0.800 A)(40 min)(60 s/1 min)(69.723 g/1 mol)/(96845)(3) = 0.462 g Ga
question
A current of 3.28 A is passed through a Pb(NO3)2 solution. How long, in hours, would this current have to be applied to plate out 8.60 g of lead?
Current is applied to a molten mixture of CuF, ZnCl2, and MgI2. What is produced at the cathode?
Mg, F2, Cu, Cl2, Zn, I2
What is produced at the anode?
F2, Mg, Cu, Cl2, I2, Zn
answer
The cations in the mixture (Cu+, Zn2+, and Mg2+) will all compete for reduction. The reduction potential for Cu+ is the greatest of these, so it is favored at the cathode and Cu is produced.
The anions in this mixture (F-, Cl-, and I-) will all compete for oxidation. The reduction potential for I- is the lowest of these, so it is favored at the anode and I2 is produced.
question
Consider two cells, the first with Al and Ag electrodes and the second with Zn and Ni electrodes, each in 1.00 M solutions of their ions. If connected as voltaic cells in series, which two metals are plated, and what is the total potential, E naught?
If connected in such a way that one cell acts as a battery to power the other as an electrolytic cell, which two metals are plated, and what is the total potential, E naught?
If 4.50 g of metal is plated in the voltaic cell, how much metal is plated in the electrolytic cell?
answer
Al3+ + 3e- = Al E = -1.66 V
Ag+ + e- = Ag E = +.80 V
Zn2+ + 2e- = Zn E = -0.76 V
Ni2+ + 2e- = Ni E = -0.26 V
(0.80) - (-1.66) = 2.46 V
(-0.26) - (-0.76) = 0.50 V
Ag and Ni are plated when the cells are in series.
The E naught is 2.46 + 0.50 = 2.96 V
Making one of the cells electrolytic means Ag and Ni are still plated, and the signs are simply flipped.
The E naught is 2.46 - 0.50 = 1.96 V
4.50 g(1 mol Ag/107.87 g)(1 mol/1 mol)(1 mol Zn/2 mol e-)(65.39 g Zn/1 mol) = 1.36 g Zn
question
Predict the ground-state electron configuration of each ion. Use the abbreviated noble gas notation.
answer
Cr2+: [Ar]3d^4
The neutral Cr has 24 electrons and the configuration [Ar]4s^13d^5. The s and d subshells are half-full. Cr2+ has 22 electrons.
Cu2+: [Ar]3d^9
A neutral Cu has 29 electrons and the configuration [Ar]4s^13d^10. The d subshell is full. Cu2+ has 27 electrons.
Co3+: [Ar]3d^6
A neutral Co has 27 electrons and the configuration [Ar]4s^23d^7. The Co3+ has 24 electrons.
question
Which ions have five d electrons in the outermost d sub shell?
Mn2+, Tc2+, Re2+, Ru2+, Y2+, Zn2+, Fe2+
answer
The Mn2+, Tc2+, and Re2+ ions (group 7) have five d electrons.
question
Which ions have ten d electrons in the outermost d sub shell?
Zn2+, Sc2+, Cd2+, Tc2+, Y2+, Ir2+, Fe2+
answer
The Zn2+ and Cd2+ ions (group 12) have ten d electrons.
question
Give the highest oxidation state for Cr.
answer
+6
The electron configuration for Cr is [Ar]4s^13d^5. The outermost s and d electrons can be lost to give a stable configuration of [Ar] for a total for +6 electrons.
question
For each metal compound, give the coordination number for the metal species.
[M(NH3)4Br2]
Na[Ag(CN)2]
[Cd(en)Br2]
answer
The unspecified metal species [M(NH3)4Br2] is bound to four NH3 ligands and 2 Br- ligands, so the coordination number is 6.
Na[Ag(CN)2] has only two mono dentate ligands in the brackets, so the coordination number is 2.
[Cd(en)Br2] has a bidentate and monodentate ligand: so en counts for 2 and Br has two for a coordination number of 4.
question
Classify each of the following coordination compounds according to the coordination number.
Give the oxidation state of each metal species.
Fe = Fe(CO)5 = Fe(CO)4I2
answer
Oxidation state of Fe: 0
Uncombined elements have an oxidation number of 0.
Oxidation state of Fe in Fe(CO)5: 0
The carbonyl ligands are 0, and since the complex is neutral, Fe must also be 0.
Oxidation state of Fe in Fe(CO4)I2: +2
Since there are two I with a negative charge, Fe must have an oxidation number of +2 to equal it out.
question
Which of these complexes or complex ions has geometric isomers?
[Cr(NH3)4Cl2]+
[Cr(NH3)5Cl]2+
[Co(NH3)2Cl2]2- (tetrahedral)
[Pt(NH3)2Cl2] (square planar)
answer
[Cr(NH3)4Cl2]+
The complex is octahedral, so it can form geometric isomers.
[Pt(NH3)2Cl2]
The complex is square planar so it can form geometric isomers.
question
Indicate how many stereoisomers are possible for each compound.
square planar [Pt(NH3)2Cl2]
tetrahedral [NiCl2Br2]2-
octahedral [Fe(CO)4Cl2]
answer
A square planar complex with two mono dentate ligands can exist as a cis or trans isomer, so it has two possible stereoisomers.
A tetrahedral complex with mono dentate ligands can only exist as one stereoisomer.
An octahedral complex generally can exist as a cis or trans isomer, so it has two possible stereoisomers.
question
Determine the overall charge on each complex.
hexafluoraluminate(III)
tetraaquadichlorochromium(III)
diaquadichloroethylenediaminecobalt(III)
answer
-3
+1
+1
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