Question 1

In the voltaic cell: $$Sn_{(s)} | Sn(NO_3$)_2_{(aq)} || Al_2$(SO_4$)_3_{(aq)} | Al_{(s)}$$, which species is the cathode?

Accepted Answer

$$Sn_{(s)}$$

Question 2

Given the cell reaction $$Sn^{2+} + 2e$$^- \rightarrow Sn$$, what is the corresponding anode reaction?

Accepted Answer

$$Al_{(s)} \rightarrow Al$$^{3+}$$ + 3e^-$$

Question 3

If the $$E_{cell}$$ for a voltaic cell is $$1.52\,V$$, what can you conclude about the spontaneity of the reaction?

Accepted Answer

The reaction is spontaneous.

Question 4

If the size of the electrodes in a voltaic cell is doubled, what happens to the $$E_{cell}$$ value?

Accepted Answer

It remains unchanged.

Question 5

During electroplating, does the thin electrode gain or lose mass?

Accepted Answer

Gain

Question 6

For the $$KBr_{aq}$$ electrolytic cell, the $$E_{cell}$$ value is $$-1.90\,V. $$What does this indicate about the reaction?

Accepted Answer

The reaction is non-spontaneous and requires external energy.

Question 7

In the $$KBr_{aq}$$ electrolytic cell, which equation represents the cathode reaction?

Accepted Answer

$$2H_2O_{(l)} + 2e^- \rightarrow H_2_{(g)} + 2OH^-_{(aq)}$$

Question 8

A silver nitrate electrolytic cell uses a current of $$15.6\,A$$ for $$2.78$$ hours. Calculate the number of moles of electrons transferred. ($$F = 9.65 	imes 10^4$\,C/mol)$$

Accepted Answer

$$1.62\,mol$$

Question 9

In the silver nitrate cell above, how many grams of silver are deposited if $$1.62\,mol of $$electrons are transferred? ($$M_{Ag} = 107.87\,g/mol)$$

Accepted Answer

$$14.6\,g$$

Question 10

What is the correct formula to calculate the number of moles of electrons transferred in an electrolytic cell?

Accepted Answer

$$n_e = \dfrac{It}{F}$$

Question 11

How long (in minutes) would it take to plate $$2.21\,g of $$nickel from a $$NiCl_2$$ solution using a current of $$3.20\,A$$? ($$M_{Ni} = 58.69\,g/mol$$, $$F = 9.65 	imes 10^4$\,C/mol)$$

Accepted Answer

$$37.8\,min$$

Question 12

Which of the following is the correct anode reaction for the nickel plating process?

Accepted Answer

$$Ni_{(s)} \rightarrow Ni$$^{2+}$$_{(aq)} + 2e^-$$

Question 13

If a cell has $$E_{cell} \u003c 0$$, which of the following is true?

Accepted Answer

The cell requires an external power source to operate.

Question 14

Which of the following best explains why increasing the current in an electrolytic cell increases the rate of metal deposition?

Accepted Answer

A higher current increases the number of electrons available for reduction per unit time.

Question 15

In an electrolytic cell, which electrode is the site of oxidation?

Accepted Answer

Anode

Question 16

Which of the following is a correct application of Faraday's Law in electroplating?

Accepted Answer

The mass of metal deposited is directly proportional to the total charge passed through the cell.

Question 17

A student claims that doubling the time of electrolysis will double the mass of metal deposited. Is this correct?

Accepted Answer

Yes, because mass is proportional to time according to Faraday's Law.

Electrochemistry and Electroplating: Study Notes

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