Worksheet: Charge Transfer in Electrolysis

In this worksheet, we will practice calculating the total amount of charge transferred during electrochemical processes such as electroplating.

Q1:

What is the charge of a mole of electrons? The charge of a single electron is 1.60×10 C .

  • A 3 . 7 6 × 1 0 C
  • B 8 . 6 3 × 1 0 C
  • C 1 . 1 6 × 1 0 C
  • D 9 . 6 3 × 1 0 C
  • E 2 . 6 6 × 1 0 C

Q2:

The reduction of aluminum ions is described by the ionic half-equation: Al()+3eAl()3+ls. What charge must be delivered to reduce 200 kg of aluminum ions to aluminum metal? The charge of a single electron is 1.602×10 C.

  • A 2 . 1 5 × 1 0 C
  • B 4 . 4 5 × 1 0 C
  • C 6 . 1 1 × 1 0 C
  • D 1 . 8 6 × 1 0 C
  • E 7 . 1 3 × 1 0 C

Q3:

The reduction of lithium ions can be represented by the ionic half-equation: Li()+eLi()+ls.

How many electrons are required per lithium ion to produce lithium metal?

How many moles of electrons are required to reduce 1.00 g of lithium ions?

How much charge must be delivered to reduce 1.00 g of lithium ions? The charge of a single electron is 1.602×10 C.

  • A 9 . 6 3 × 1 0 C
  • B 1 . 8 7 × 1 0 C
  • C 6 . 7 4 × 1 0 C
  • D 3 . 2 1 × 1 0 C
  • E 1 . 3 8 × 1 0 C

Q4:

How long would it take to reduce 1 mole of Cr5+ to Cr()s using a current of 33.5 A? Assume the voltage is sufficient to perform the reduction.

Q5:

How long would it take to reduce 1 mole of Au3+ to Au()s using a current of 4.01 A? Assume the voltage is sufficient to perform the reduction.

Q6:

What mass of calcium is produced in the electrolysis of molten CaCl2 if a total charge of 3.33×10 C passes through the cell? Assume the voltage is sufficient to perform the reduction and that the efficiency is 100%.

Q7:

What mass of lithium is produced in the electrolysis of molten LiH if a total charge of 3.33×10 C passes through the cell? Assume the voltage is sufficient to perform the reduction and that the efficiency is 100%.

Q8:

What mass of aluminum is produced in the electrolysis of molten AlCl3 if a total charge of 3.33×10 C passes through the cell? Assume the voltage is sufficient to perform the reduction and that the efficiency is 100%.

Q9:

What mass of chromium is produced in the electrolysis of molten CrBr3 if a total charge of 3.33×10 C passes through the cell? Assume the voltage is sufficient to perform the reduction and that the efficiency is 100%.

Q10:

How long would it take to reduce 1 mole of Al3+ using a current of 1.057 A? Assume the voltage is sufficient to perform the reduction.

Q11:

How long would it take to reduce 1 mole of Ca2+ using a current of 19.8 A? Assume the voltage is sufficient to perform the reduction.

Q12:

In one process used for electroplating silver, a current of 10.23 A was passed through an electrolytic cell for exactly 1 hour.

How many moles of electrons passed through the cell?

What mass of silver was deposited at the cathode?

Q13:

Aluminum metal can be made from aluminum ions by electrolysis. What mass of aluminum metal would be recovered if a current of 2.50×10 A passed through the solution for 15.0 minutes? Assume the yield is 100%.

Q14:

In one application, a 0.010 mm layer of chromium must be deposited on a part with a total surface area of 3.3 m2 from a solution containing chromium(III) ions. How long would it take to deposit the layer of chromium if the current was 33.46 A? The density of chromium (metal) is 7.19 g/cm3.

Q15:

The top of a 3.00×5.50mm sheet of iron is galvanized to a thickness of 0.100 mm of zinc. The density of zinc is 7.140 g/cm3.

What mass of zinc is required?

If the zinc comes from a solution of Zn(NO)32 and the current is 25.5 A, how long will it take to galvanize the top of the iron?

Q16:

An irregularly shaped metal part made from a particular alloy was galvanized with zinc using a Zn(NO)32 solution. When a current of 2.399 A was used, it took exactly 1 hour to deposit a 0.01323 mm layer of zinc on the part. What was the total surface area of the part? The density of zinc is 7.140 g/cm3. Assume the efficiency is 100%.

Q17:

The current in a circuit is 2.5 A. To 2 significant figures, how many coulombs of charge pass through the circuit in 35 minutes?

  • A 7 . 1 × 1 0 C
  • B88 C
  • C4.3 C
  • D 5 . 3 × 1 0 C
  • E14 C

Q18:

If the current in a circuit is 3.5 A, how many moles of electrons pass through the circuit in 45 minutes?

  • A 1 . 1 × 1 0 mol
  • B 2 . 8 × 1 0 mol
  • C 9 . 8 × 1 0 mol
  • D 3 . 9 × 1 0 mol
  • E 1 . 6 × 1 0 mol

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