4E Electrolysis Quiz

Two circuits are shown. The light bulb lights up in only one of the circuits. What is the identity of X?

• barium sulfate

• calcium

• potassium bromide

• zinc

Answer explanation

A metal can conduct electricity in solid state.

Calcium react with water to form calcium hydroxide which can then conduct electricity when in aqueous state.

In which electrolysis experiment would there be no change in pH of the solution when inert electrodes are used?

• aqueous copper (II) nitrate

• aqueous silver sulfate

• concentrated copper (II) chloride solution

• concentrated potassium bromide solution

Answer explanation

at the cathode: copper (II) ions are discharge

at the anode: chloride ions are discharge (because the solution is concentrated)

The diagram shows the electrolysis of dilute sodium chloride solution using inert electrodes.

Given that, at room temperature and pressure, x moles of electrons were passed in the circuit, which of the following statement is correct?

• 6x dm³ of oxygen was collected at the anode.

• 6x dm³ of hydrogen was collected at the cathode.

• 12x dm³ of oxygen was collected at the cathode.

• 12x dm³ of hydrogen was collected at the anode

Answer explanation

At the anode: hydroxide is discharge.

4OH^- -> O₂ + 2H₂O + 4e^-

Mole ratio of electron to oxygen is 4 : 1.

no of moles of oxygen = x/4

volume of oxygen = x / 4 x 24dm³ = 6x dm³

Aqueous copper(II) sulfate is electrolysed using copper electrodes. The current is constant and the anode is weighed at regular time intervals.

Which graph is obtained when the mass of the anode is plotted against time?

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The chloride of metal X is dissolved in water. A concentrated solution of this chloride is electrolysed using inert electrodes, Y and Z. X is above sodium in the reactivity series.

In addition to chlorine, which gas is liberated and at which electrode?

• Hydrogen is discharged at Y.

• Hydrogen is discharged at Z.

• Oxygen is discharged at Y.

• Oxygen is discharged at Z.

Answer explanation

Y is the anode and Z is the cathode.

Hydrogen is discharged at the cathode.

In which set of apparatus is the metal key electroplated with copper?

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When electrolysed using inert electrodes, which dilute solution would produce the greatest increase in mass at the cathode?

• Aluminium sulfate

• Copper (II) sulfate

• Lead (II) nitrate

• Silver nitrate

Answer explanation

Ag just needs to gain 1 electron

Which pair of metals X and Y will produce the highest voltage when used as electrodes in a simple cell?

• X: copper

  Y: silver

• X: magnesium

  Y: silver

• X: magnesium

  Y: zinc

• X: zinc

  Y: copper

The electrolysis set-up shown below is not complete.

Which diagram should be shown at X when the solution has undergone electrolysis for a few minutes?

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In an electrolysis experiment, the same amount of charge deposited 6.0 g of titanium and 7.0 g of iron. The charge on the iron ion was +2.

What is the charge on the titanium ion?

[A_r : Ti, 48;  Fe, 56]

• +1

• +2

• +3

• +4