(a) Determine the oxidation number of manganese in MnO\(_4\) (b)(i) List two metals that are extracted from their ores by electrolysis (ii) Give one differe...
Question 1 Report
(a) Determine the oxidation number of manganese in MnO\(_4\)
(b)(i) List two metals that are extracted from their ores by electrolysis
(ii) Give one difference between a conductor and an electrolyte.
Answer Details
(a) Oxidation number of manganese in the tetraoxomanganate(VII) ion, \(MnO_4^-\).
Let the oxidation number of Mn be \(x\). Each oxygen is \(-2\) and the overall charge on the ion is \(-1\):
\[x + 4(-2) = -1\]
\[x - 8 = -1\]
\[x = +7\]
So manganese has an oxidation number of +7.
(b)(i) Two metals extracted from their ores by electrolysis: sodium and aluminium. (Potassium, calcium and magnesium are also acceptable, as they are all high in the electrochemical series.)
(ii) Difference between a conductor and an electrolyte:
| Conductor | Electrolyte |
|---|---|
| Conducts electricity by means of free electrons. | Conducts electricity by means of free-moving ions. |
| Is not chemically changed (decomposed) by the current. | Undergoes chemical decomposition when the current flows. |
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