Write the reaction when electric current is passed through molten sodium chloride
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3. The electrolysis of sodium chloride solution (brine) and molten sodium chloride
The electrolysis of aqueous sodium chloride (often referred to as 'brine' solution) is described in terms of apparatus and products formed. What are the products of the electrolysis of aqueous sodium chloride solution (brine)?
Reminders: Electrolysis (of sodium chloride) is a way of splitting up (decomposition) of the compound (sodium) using electrical energy. The electrical energy comes from a d.c. (direct current) battery or power pack supply. A conducting liquid, containing ions, called the electrolyte (molten or aqueous sodium chloride) must contain the compound (sodium chloride) that is being broken down. The electricity must flow through electrodes dipped into the electrolyte, to complete the electrical circuit with the battery. Electrolysis can only happen when the circuit is complete, and an electrical current (electricity) is flowing, then the products of electrolysing aqueous sodium chloride solution (brine) OR molten sodium chloride are released on the electrode surfaces where they can be collected. Electrolysis always involves a flow of electrons in the external wires and electrodes and a flow of ions in the electrolyte and there is always a reduction at the negative cathode electrode (which attracts positive ions, cations) and an oxidation at the positive anode electrode (which attracts negative ions, anions) and it is the ions which are discharged to give the products. These revision notes on the electrolysis of aqueous sodium chloride solution (electrolysis of brine) should prove useful for the new AQA chemistry, Edexcel chemistry & OCR chemistry GCSE (9–1, 9-5 & 5-1) science courses.
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3. The electrolysis of sodium chloride solution (brine)
Aqueous solutions with inert electrodes (carbon or platinum)
The products of electrolysing aqueous sodium chloride solution are hydrogen gas, chlorine gas and sodium hydroxide solution
The simple apparatus illustrated on the right can be used in simple school or college experiments for the electrolysis of sodium chloride solution (often referred to as 'brine' in the chemical industry). The graphite (carbon) electrodes are, through a large rubber bung, 'upwardly' dipped into an solution of the sodium chloride solution (the electrolyte).
The cell can be made from plastic pipe and a big rubber bung with two holes in it. In the simple apparatus the gaseous products (hydrogen and chlorine) are collected in small test tubes inverted over the carbon electrodes and chemical tests performed on them. You have to fill the little test tubes with the electrolyte (sodium chloride solution), hold the liquid in with your finger and carefully invert them over the nearly full electrolysis cell.
A more elaborate format is to use a Hoffman Voltameter (above left diagram) using platinum electrodes and accurately calibrated collecting tubes like burettes. The Hofmann voltammeter is filled with the electrolyte (aqueous sodium chloride solution) by opening the taps at the top of the outer tubes to allow any gas to escape. The gases formed on the electrolysis of the dilute 'brine' solution can be collected via the same taps. The students should note that nothing happens until you switch on the electricity supply (see simple animation above!). The platinum or carbon electrodes are inert.
The industrial electrodes must be made of an inert material like platinum/titanium which is not attacked by chlorine or alkali, but in the school /college laboratory, the Hofmann voltammeter is a good demonstration (platinum electrodes) and the 'simple cell' for students uses carbon/graphite electrodes which are reasonably inert.
However a simple cell using carbon electrodes can be used by students/pupils to demonstrate the industrial process in the laboratory and the simple apparatus (above right) can also be used in schools using two inert wire electrodes.
The electrolysis will only take place when electricit
The electrolysis of aqueous sodium chloride (often referred to as 'brine' solution) is described in terms of apparatus and products formed. What are the products of the electrolysis of aqueous sodium chloride solution (brine)?
Reminders: Electrolysis (of sodium chloride) is a way of splitting up (decomposition) of the compound (sodium) using electrical energy. The electrical energy comes from a d.c. (direct current) battery or power pack supply. A conducting liquid, containing ions, called the electrolyte (molten or aqueous sodium chloride) must contain the compound (sodium chloride) that is being broken down. The electricity must flow through electrodes dipped into the electrolyte, to complete the electrical circuit with the battery. Electrolysis can only happen when the circuit is complete, and an electrical current (electricity) is flowing, then the products of electrolysing aqueous sodium chloride solution (brine) OR molten sodium chloride are released on the electrode surfaces where they can be collected. Electrolysis always involves a flow of electrons in the external wires and electrodes and a flow of ions in the electrolyte and there is always a reduction at the negative cathode electrode (which attracts positive ions, cations) and an oxidation at the positive anode electrode (which attracts negative ions, anions) and it is the ions which are discharged to give the products. These revision notes on the electrolysis of aqueous sodium chloride solution (electrolysis of brine) should prove useful for the new AQA chemistry, Edexcel chemistry & OCR chemistry GCSE (9–1, 9-5 & 5-1) science courses.
My ELECTROCHEMISTRY INDEX
3. The electrolysis of sodium chloride solution (brine)
Aqueous solutions with inert electrodes (carbon or platinum)
The products of electrolysing aqueous sodium chloride solution are hydrogen gas, chlorine gas and sodium hydroxide solution
The simple apparatus illustrated on the right can be used in simple school or college experiments for the electrolysis of sodium chloride solution (often referred to as 'brine' in the chemical industry). The graphite (carbon) electrodes are, through a large rubber bung, 'upwardly' dipped into an solution of the sodium chloride solution (the electrolyte).
The cell can be made from plastic pipe and a big rubber bung with two holes in it. In the simple apparatus the gaseous products (hydrogen and chlorine) are collected in small test tubes inverted over the carbon electrodes and chemical tests performed on them. You have to fill the little test tubes with the electrolyte (sodium chloride solution), hold the liquid in with your finger and carefully invert them over the nearly full electrolysis cell.
A more elaborate format is to use a Hoffman Voltameter (above left diagram) using platinum electrodes and accurately calibrated collecting tubes like burettes. The Hofmann voltammeter is filled with the electrolyte (aqueous sodium chloride solution) by opening the taps at the top of the outer tubes to allow any gas to escape. The gases formed on the electrolysis of the dilute 'brine' solution can be collected via the same taps. The students should note that nothing happens until you switch on the electricity supply (see simple animation above!). The platinum or carbon electrodes are inert.
The industrial electrodes must be made of an inert material like platinum/titanium which is not attacked by chlorine or alkali, but in the school /college laboratory, the Hofmann voltammeter is a good demonstration (platinum electrodes) and the 'simple cell' for students uses carbon/graphite electrodes which are reasonably inert.
However a simple cell using carbon electrodes can be used by students/pupils to demonstrate the industrial process in the laboratory and the simple apparatus (above right) can also be used in schools using two inert wire electrodes.
The electrolysis will only take place when electricit
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Answer:
When current is passed through molten sodium chloride, Na+ ions get reduced at the negative electrode (cathode) and thus sodium is deposited at cathode whereas Cl− ions get oxidized at the positive electrode (anode) and hence chlorine gas is formed at anode.
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