A shipyard produces sodium metal from molten sodium chloride. Fig. 1 shows a protected industrial cell. The sodium is kept away from water because it reacts...
Question 1 Report
A shipyard produces sodium metal from molten sodium chloride. Fig. 1 shows a protected industrial cell. The sodium is kept away from water because it reacts violently with water. Table 1 compares the melting points of two substances used at the site.
| Substance | Melting point / degrees C |
|---|---|
| Sodium chloride | 801 |
| Sodium metal | 98 |
(a) Name the particles that move to the negative electrode in molten sodium chloride. [1]
(b) Describe what happens to chloride ions at the positive electrode. [1]
(c) Explain why solid sodium chloride cannot be electrolysed. [2]
(d) Use Table 1 to state why the cell is operated above 801 degrees C. [1]
Answer Details
(a) Sodium ions, \(\text{Na}^+\), move to the negative electrode. [1]
(b) Chloride ions lose electrons at the positive electrode. They are oxidised to form chlorine molecules. [1]
(c) In solid sodium chloride, ions are fixed in a lattice. They cannot move to carry charge, so electrolysis cannot occur. [2]
(d) The cell is operated above 801 degrees C to melt the sodium chloride. [1]
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