Question 1

A hydrogen fuel cell depends on ________

Accepted Answer

A hydrogen fuel cell depends on the redox chemistry of hydrogen, where the oxidation of hydrogen at the anode and the reduction of oxygen at the cathode produce electricity and water.

Question 2

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction as written? 2CH₃OH + 3O₂ $\rightarrow$2CO₂ + 3H₂O

Accepted Answer

In the reaction, each methanol (CH3OH) molecule is oxidized to CO2, transferring 6 electrons per molecule. Since there are 2 methanol molecules, a total of 12 electrons are transferred.

Question 3

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction per mole of methanol consumed? 2CH₃OH + 3O₂ $\rightarrow$2CO₂ + 3H₂O

Accepted Answer

In this reaction, 6 electrons are transferred per mole of methanol consumed. This can be seen by noting the change in oxidation states of the carbon atoms in methanol, from +1 to +4, indicating the loss of 6 electrons. Conversely, the oxygen in oxygen gas is reduced from 0 to -2, indicating the gain of 6 electrons. Therefore, the answer is 6, as in choice B.

Question 4

Applying a current to a rechargeable battery converts it from ________ cell to ________ cell.

Accepted Answer

The answer of Applying a current to a rechargeable battery...

Question 5

If in using a lead-acid battery to start a car, 1.00 gram of Pb is consumed on the anode, how long will it take to recharge the battery, using a current of 0.500 amperes, and turn the PbSO₄ that was produced back into Pb?

Accepted Answer

The reaction that occurs at the anode during discharge is:

Pb(s) + SO4^2-(aq) → PbSO4(s) + 2e^-

This means that for every 2 electrons produced, 1 Pb atom is consumed. Since the problem says that 1.00 g of Pb is consumed, we need to find out how many electrons this corresponds to:

1.00 g Pb * (1 mol Pb/207.2 g Pb) * (2 mol e^-/1 mol Pb) * (6.022 x 10^23 e^-/1 mol e^-) = 5.81 x 10^21 e^-

Now we can use Faraday's Law to find out how long it will take to deposit this many electrons onto the cathode during the recharge process:

Q = nF

where Q is the total charge (in coulombs), n is the number of electrons, and F is the Faraday constant (96485 C/mol e^-).

Q = (5.81 x 10^21 e^-) * (96485 C/mol e^-) = 5.60 x 10^25 C

I = Q/t

where I is the current (in amperes), Q is the total charge (in coulombs), and t is the time (in seconds).

t = Q/I = (5.60 x 10^25 C) / (0.500 A) = 1.12 x 10^26 s

Finally, we convert seconds to minutes:

1.12 x 10^26 s * (1 min/60 s) = 1.87 x 10^24 min

Round this to one significant figure and we get:

Answer: C) 31.1 min

Question 6

The oxidation of hydrogen by oxygen is one of the most-used reactions in fuel-cell technology. The overall reaction, which is given below, has a $\Delta$G° value of -474 kJ/mol. What is the standard cell potential for this fuel cell? 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O(l)

Accepted Answer

The standard cell potential ($E°$) can be calculated using the formula $\Delta G° = -nFE°$, where $n$ is the number of moles of electrons transferred (4 for this reaction), $F$ is Faraday's constant (96485 C/mol), and $\Delta G°$ is given as -474 kJ/mol. Solving for $E°$ gives approximately 1.23 V.

Question 7

How long would it take to electroplate a flute with 28.3 g of silver at a constant current of 2)0 amps using AgNO₃?

Accepted Answer

The correct formula for silver nitrate is likely intended to be AgNO3, but the provided formula seems to be a typographical error. To calculate the time required for electroplating, we use Faraday's laws of electrolysis. The molar mass of silver (Ag) is 107.8682 g/mol, and the charge required to reduce one mole of Ag+ ions is 96,485 C (Coulombs) because silver has a valency of 1. First, calculate the moles of silver to be plated:$$ \text{Moles of Ag} = \frac{28.3 \text{ g}}{107.8682 \text{ g/mol}} $$$$ \text{Moles of Ag} = 0.2624 \text{ mol} $$Next, calculate the total charge needed:$$ \text{Charge} = \text{Moles of Ag} \times \text{Charge per mole of Ag} $$$$ \text{Charge} = 0.2624 \text{ mol} \times 96,485 \text{ C/mol} $$$$ \text{Charge} = 25,336 \text{ C} $$Finally, calculate the time required using the current:$$ \text{Time} = \frac{\text{Charge}}{\text{Current}} $$$$ \text{Time} = \frac{25,336 \text{ C}}{2.0 \text{ A}} $$$$ \text{Time} = 12,668 \text{ s} $$To convert seconds to minutes:$$ \text{Time} = \frac{12,668 \text{ s}}{60 \text{ s/min}} $$$$ \text{Time} \approx 211 \text{ min} $$Therefore, it would take approximately 211 minutes to electroplate the flute with 28.3 g of silver at a constant current of 2.0 amps.

Question 8

Aluminum metal is refined in a very energy-intensive process from bauxite ore using the Hall process, which requires electrolysis of aluminum oxide, Al₂O₃, in molten cryolite at more than 1,012°C. In an industrial electrolysis cell, 1,900 kg of aluminum oxide was reduced with a current of 1,500 amps. How long did it take to reduce all the reactant to aluminum metal?

Accepted Answer

The answer of Aluminum metal is refined in a very...

Question 9

The oxidation of methanol, as described by the equation below, has a $\Delta$G° value of -937.9 kJ/mol. What is the standard cell potential for a methanol fuel cell? 2CH₃OH + 3O₂ $\rightarrow$ 2 CO₂ + 3H₂O

Accepted Answer

The standard cell potential can be calculated using the equation:
∆G° = -nFE°cell
where n is the number of electrons transferred in the reaction, F is the Faraday constant (96,485 C/mol), and E°cell is the standard cell potential.

In this case, the oxidation of methanol involves the transfer of 6 electrons, so n = 6. Plugging in the given ∆G° value (-937.9 kJ/mol) and the appropriate constants, we get:

-937.9 kJ/mol = -(6)(96,485 C/mol)(E°cell)
E°cell = 0.810 V

Therefore, the standard cell potential for a methanol fuel cell is 0.810 V.

Question 10

The oxidation of hydrogen by oxygen is one of the most-used reactions in fuel-cell technology. The overall reaction, which is given below, has a $\Delta$G° value of -237 kJ/mol. What is the standard cell potential for this fuel cell? H₂(g) + $\frac { 1 } { 2 }$O₂(g) $\rightarrow$ H₂O(l)

Accepted Answer

The standard cell potential (E°) can be calculated using the formula $\Delta G° = -nFE°$, where n is the number of moles of electrons transferred (2 for this reaction), F is Faraday's constant (96485 C/mol), and $\Delta G°$ is given as -237 kJ/mol. Solving for E° gives approximately 1.23 V.

Question 11

Bubbles will form on wires attached to a 9-volt battery placed in water. Which statements correctly describe what is happening?
I. The wire attached to the (-) battery electrode becomes the cathode, and water is being reduced there to produce hydrogen gas.
II. The wire attached to the (+) battery electrode becomes the anode, and water is being oxidized there to produce oxygen gas.
III. The wire attached to the (-) battery electrode becomes the cathode, and water is being oxidized there to produce oxygen gas.
IV. The wire attached to the (+) battery electrode becomes the anode, and water is being reduced there to produce hydrogen gas.

Accepted Answer

In electrolysis, the cathode is the negative electrode where reduction occurs, producing hydrogen gas. The anode is the positive electrode where oxidation occurs, producing oxygen gas.

Question 12

For a chemical reaction to be considered for use in a fuel cell, it is absolutely essential for the ________

Accepted Answer

For a chemical reaction to be considered for use in a fuel cell, the free-energy change must be negative. This means that the reaction releases energy as it proceeds, which can be harnessed to generate electricity in a fuel cell. Reactants can be solids, liquids, or gases, as long as the free-energy change is negative.

Question 13

How do fuel cells differ from traditional electrochemical cells (batteries)?

Accepted Answer

Fuel cells differ from traditional electrochemical cells (batteries) in that the supply of reactants is continually renewed in fuel cells, whereas in batteries, the reactants are consumed until the battery is depleted and needs to be recharged or replaced.

Question 14

Copper metal is purified by electrolysis. How much copper metal could be produced from copper(II) oxide by applying a current of 10.0 amps at the appropriate negative potential for
12)0 hours?

Accepted Answer

The amount of copper metal produced can be calculated using Faraday's constant (F) and the equation:
moles of electrons transferred = current (in amperes) × time (in seconds) ÷ Faraday's constant
Using the molar mass of CuO and stoichiometry, we can convert moles of electrons to moles of CuO, and then to mass of Cu:
CuO + H2O → Cu + O2 + H2O
1 mol e^- (or 1 F) transfers 2 mol of Cu:
2 mol Cu / 1 mol e^-
The appropriate negative potential for the reduction of CuO is -0.34 V (from a table of standard reduction potentials).
F = 96485 C/mol e^- (or 96485 A·s/mol e^-)
10.0 A × (12.0 h × 3600 s/h) = 4.32 × 10^5 C
moles of electrons transferred = 4.32 × 10^5 C ÷ 96485 C/mol e^- = 4.48 mol e^-
moles of Cu produced = 0.5 × 4.48 mol e^- = 2.24 mol Cu
mass of Cu produced = 2.24 mol × 63.55 g/mol = 142 g

Question 15

Bubbles will form on wires attached to a 9-volt battery placed in water. What is happening here?

Accepted Answer

The water is being reduced on the wire attached to the (-) battery electrode and oxidized on the wire attached to the (+) battery electrode.

Question 16

Chromium often is electroplated on other metals and even plastics to produce a shiny metallic appearance. How many grams of chromium would plate out from a solution of Cr(NO₃)₃ when 10 amps of current are passed through the electrolytic cell for 5.36 hours?

Accepted Answer

The answer of Chromium often is electroplated on other metals...

Question 17

How many kilograms of aluminum metal can be produced by the electrolysis of Al₂O₃ using a current of 100 amperes for 24 hours?

Accepted Answer

To calculate the amount of aluminum produced, we need to use Faraday's laws of electrolysis, which states that the amount of metal deposited during electrolysis is directly proportional to the amount of electricity passed through the solution.

We can use the formula, 
Amount of metal deposited = (Current x Time) / (96500 x Number of electrons required for the reaction)

For aluminum, the number of electrons required for the reaction is 3.

Number of moles of Al = (100 A x 24 hrs) / (96500 C/mol x 3 e-)

Number of moles of Al = 0.088 mol

The molar mass of Al = 27 g/mol

Therefore mass of Al = 0.088 mol x 27 g/mol
Mass of Al = 2.376 g

Converting grams to kilograms,
Mass of Al = 0.002376 kg

Therefore, the answer is A) 0.81 kg.

Question 18

Consider the following standard reduction potentials. $$\begin{array} { | l | c | } 
\hline { \text { Reduction Half-Reaction } } & \mathbf { E } ^ { 0 } \text { (volts) } \
\hline \mathrm { Fe } ^ { 2 + } ( a q ) + 2 \mathrm { e } ^ { - } \longrightarrow \mathrm { Fe } ( s ) & - 0.45 \
\hline \mathrm { Cu } ^ { 2 + } ( a q ) + 2 \mathrm { e } ^ { - } \longrightarrow \mathrm { Cu } ( s ) & + 0.34 \
\hline \mathrm { Zn } ^ { 2 + } ( a q ) + 2 \mathrm { e } ^ { - } \longrightarrow \mathrm { Zn } ( s ) & - 0.76 \
\hline \mathrm { Al } ^ { 3 + } ( a q ) + 3 \mathrm { e } ^ { - } \longrightarrow \mathrm { Al } ( s ) & - 1.66 \
\hline \mathrm { Sn } ^ { 2 + } ( a q ) + 2 \mathrm { e } ^ { - } \longrightarrow \mathrm { Sn } ( s ) & - 0.14 \
\hline
\end{array}$$ Which corrosion reaction when two metals come in contact is not likely to occur?

Accepted Answer

The reduction potential for aluminum ions is much lower than that for iron ions, making the reduction of aluminum ions less favorable compared to the oxidation of iron.

Question 19

Cathodic protection occurs when iron is ________

Accepted Answer

Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. This is achieved by attaching the metal to be protected to a more electroactively sacrificial metal (anode), which is oxidized instead of the protected metal.

Question 20

Which one of the following statements about the recharging of a voltaic cell is not correct? When a voltaic cell is recharged, it is run as an electrolytic cell.

Accepted Answer

The statement that the magnitude of the external voltage must be exactly the same as the cell potential is not correct. In recharging a voltaic cell, the external voltage applied must be greater than the cell potential to drive the reverse reactions.

Quiz 19: Electrochemistry: the Quest for Clean Energy

A hydrogen fuel cell depends on ________

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction as written? 2CH₃OH + 3O₂ $\rightarrow$ 2CO₂ + 3H₂O

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction per mole of methanol consumed? 2CH₃OH + 3O₂ $\rightarrow$ 2CO₂ + 3H₂O

Applying a current to a rechargeable battery converts it from cell to cell.

If in using a lead-acid battery to start a car, 1.00 gram of Pb is consumed on the anode, how long will it take to recharge the battery, using a current of 0.500 amperes, and turn the PbSO₄ that was produced back into Pb?

The oxidation of hydrogen by oxygen is one of the most-used reactions in fuel-cell technology. The overall reaction, which is given below, has a $\Delta$ G° value of -474 kJ/mol. What is the standard cell potential for this fuel cell? 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O(l)

How long would it take to electroplate a flute with 28.3 g of silver at a constant current of 2) 0 amps using AgNO₃?

The oxidation of methanol, as described by the equation below, has a $\Delta$ G° value of -937.9 kJ/mol. What is the standard cell potential for a methanol fuel cell? 2CH₃OH + 3O₂ $\rightarrow$ 2 CO₂ + 3H₂O

The oxidation of hydrogen by oxygen is one of the most-used reactions in fuel-cell technology. The overall reaction, which is given below, has a $\Delta$ G° value of -237 kJ/mol. What is the standard cell potential for this fuel cell? H₂(g) + $\frac { 1 } { 2 }$ O₂(g) $\rightarrow$ H₂O(l)

For a chemical reaction to be considered for use in a fuel cell, it is absolutely essential for the ________

How do fuel cells differ from traditional electrochemical cells (batteries) ?

Copper metal is purified by electrolysis. How much copper metal could be produced from copper(II) oxide by applying a current of 10.0 amps at the appropriate negative potential for 12) 0 hours?

Bubbles will form on wires attached to a 9-volt battery placed in water. What is happening here?

Chromium often is electroplated on other metals and even plastics to produce a shiny metallic appearance. How many grams of chromium would plate out from a solution of Cr(NO₃) ₃ when 10 amps of current are passed through the electrolytic cell for 5.36 hours?

How many kilograms of aluminum metal can be produced by the electrolysis of Al₂O₃ using a current of 100 amperes for 24 hours?

Cathodic protection occurs when iron is ________

Which one of the following statements about the recharging of a voltaic cell is not correct? When a voltaic cell is recharged, it is run as an electrolytic cell.

Quiz 19: Electrochemistry: the Quest for Clean Energy

A hydrogen fuel cell depends on ________

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction as written? 2CH3OH + 3O2 →\rightarrow→ 2CO2 + 3H2O

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction per mole of methanol consumed? 2CH3OH + 3O2 →\rightarrow→ 2CO2 + 3H2O

Applying a current to a rechargeable battery converts it from ________ cell to ________ cell.

If in using a lead-acid battery to start a car, 1.00 gram of Pb is consumed on the anode, how long will it take to recharge the battery, using a current of 0.500 amperes, and turn the PbSO4 that was produced back into Pb?

The oxidation of hydrogen by oxygen is one of the most-used reactions in fuel-cell technology. The overall reaction, which is given below, has a Δ\DeltaΔ G° value of -474 kJ/mol. What is the standard cell potential for this fuel cell? 2H2(g) + O2(g) →\rightarrow→ 2H2O(l)

How long would it take to electroplate a flute with 28.3 g of silver at a constant current of 2) 0 amps using AgNO3?

The oxidation of methanol, as described by the equation below, has a Δ\DeltaΔ G° value of -937.9 kJ/mol. What is the standard cell potential for a methanol fuel cell? 2CH3OH + 3O2 →\rightarrow→ 2 CO2 + 3H2O

For a chemical reaction to be considered for use in a fuel cell, it is absolutely essential for the ________

How do fuel cells differ from traditional electrochemical cells (batteries) ?

Copper metal is purified by electrolysis. How much copper metal could be produced from copper(II) oxide by applying a current of 10.0 amps at the appropriate negative potential for 12) 0 hours?

Bubbles will form on wires attached to a 9-volt battery placed in water. What is happening here?

Chromium often is electroplated on other metals and even plastics to produce a shiny metallic appearance. How many grams of chromium would plate out from a solution of Cr(NO3) 3 when 10 amps of current are passed through the electrolytic cell for 5.36 hours?

How many kilograms of aluminum metal can be produced by the electrolysis of Al2O3 using a current of 100 amperes for 24 hours?

Cathodic protection occurs when iron is ________

Which one of the following statements about the recharging of a voltaic cell is not correct? When a voltaic cell is recharged, it is run as an electrolytic cell.

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction as written? 2CH₃OH + 3O₂ $\rightarrow$ 2CO₂ + 3H₂O

Methanol fuel cells depend on the following reaction. How many electrons are transferred in this redox reaction per mole of methanol consumed? 2CH₃OH + 3O₂ $\rightarrow$ 2CO₂ + 3H₂O

Applying a current to a rechargeable battery converts it from cell to cell.

If in using a lead-acid battery to start a car, 1.00 gram of Pb is consumed on the anode, how long will it take to recharge the battery, using a current of 0.500 amperes, and turn the PbSO₄ that was produced back into Pb?

The oxidation of hydrogen by oxygen is one of the most-used reactions in fuel-cell technology. The overall reaction, which is given below, has a $\Delta$ G° value of -474 kJ/mol. What is the standard cell potential for this fuel cell? 2H₂(g) + O₂(g) $\rightarrow$ 2H₂O(l)

How long would it take to electroplate a flute with 28.3 g of silver at a constant current of 2) 0 amps using AgNO₃?

The oxidation of methanol, as described by the equation below, has a $\Delta$ G° value of -937.9 kJ/mol. What is the standard cell potential for a methanol fuel cell? 2CH₃OH + 3O₂ $\rightarrow$ 2 CO₂ + 3H₂O

Chromium often is electroplated on other metals and even plastics to produce a shiny metallic appearance. How many grams of chromium would plate out from a solution of Cr(NO₃) ₃ when 10 amps of current are passed through the electrolytic cell for 5.36 hours?

How many kilograms of aluminum metal can be produced by the electrolysis of Al₂O₃ using a current of 100 amperes for 24 hours?