Electrolysis

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Question 14
Medium

This question is about electrolysis and the extraction of metals.

a.

Why can molten substances be electrolysed? Select one option:

  • Electrons can move through the molten substance to the electrodes.
  • Ions can move through the molten substance to the electrodes.
  • Protons can move through the molten substance to the electrodes.
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b.

The table below shows the products of the electrolysis of some molten ionic compounds. Complete the missing entries.

Molten compoundProduct at negative electrodeProduct at positive electrode
Copper chloride____________\text{\_\_\_\_\_\_\_\_\_\_\_\_}____________Chlorine
Lithium bromideLithium____________\text{\_\_\_\_\_\_\_\_\_\_\_\_}____________
____________\text{\_\_\_\_\_\_\_\_\_\_\_\_}____________ZincIodine
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c.

Chromium is extracted by electrolysing molten chromium(III) oxide. Balance the equation for this reaction by choosing coefficients from the list: 2, 3, 4, 5.

2Cr2O3→___Cr+___O22\text{Cr}_2\text{O}_3 \rightarrow \_\_\_ \text{Cr} + \_\_\_ \text{O}_22Cr2​O3​→___Cr+___O2​

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d.

Calculate the relative formula mass (MrM_rMr​) of chromium(III) oxide (Cr2O3\text{Cr}_2\text{O}_3Cr2​O3​). Relative atomic masses (ArA_rAr​): O=16\text{O} = 16O=16, Cr=52\text{Cr} = 52Cr=52.

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e.

The list below shows part of the reactivity series of metals, including the non-metal carbon.

A reactivity series shown as a vertical list. From top to bottom: Sodium, Calcium, Carbon, Iron, Lead, Silver. A downward-pointing arrow to the right of the list is labeled "Decreasing reactivity".

Metals can be extracted from their compounds by:

  • electrolysis
  • reduction with carbon.

Electrolysis is more expensive than reduction with carbon. Predict one metal from the list that would be extracted by each method.

  • Extracted by electrolysis:
  • Extracted by carbon reduction:
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Electrolysis Questions

  1. GCSE
  2. /Chemistry
  3. /Electrolysis