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Electrolysis Of Brine

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Electrolysis Of Brine

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    1. Electrolysis Of Brine D. Crowley, 2009

    2. Electrolysis Of Brine Thursday, June 07, 2012 To understand the electrolysis of brine (salty water)

    3. Ionic Ionic substances form when a metal reacts with a non-metal – they contain charged particles called ions For example, sodium chloride forms when sodium reacts with chlorine – it contains positively charged sodium ions and negatively charged chloride ions Ionic substances can be broken down by electricity

    4. Electrolysis Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them

    5. Electrolysis Positively charged ions move to the negative electrode during electrolysis – they receive electrons and are reduced Negatively charged ions move to the positive electrode during electrolysis – they lose electrons and are oxidised OILRIG – oxidation is loss, reduction is gain

    6. Electrolysis Products Ionic substances in solution break down into elements during electrolysis – different elements are released depending on the particular ionic substance…

    7. Negative Electrode At the negative electrode, positively charged ions gain electrons – this is reduction (ions have been reduced) Metal ions and hydrogen ions are positively charged – whether you get the metal or hydrogen during electrolysis depends on the position of the metal in the reactivity series: -

    8. Positive Electrode At the positive electrode, negatively charged ions lose electrons This is oxidation – the ions have been oxidised

    9. Ionic Compounds & Electrolysis Common ionic compounds and the elements released when their solutions are electrolysed: -

    10. Brine Brine is concentrated sodium chloride solution – if an electric current is passed through it, hydrogen gas forms at the negative electrode and chlorine gas forms at the positive electrode (a solution of sodium hydroxide forms) Sodium metal is not deposited at the negative electrode as it is too reactive for this to happen – hydrogen is given off instead…

    11. Experiment Complete the brine electrolysis experiment – write the equation for the electrolysis of brine at the cathode (-ve) and anode (+ve)

    12. Brine Sodium chloride dissolved in water is called brine – electrolysis of brine gives hydrogen at the cathode and chlorine at the anode (sodium hydroxide remains dissolved in the solution) The reactions at each electrode are ˝ equations – the ˝ equations are written so that the same number of electrons occur in each equation

    13. Brine Hydrogen ions gain electrons (reduction) to form hydrogen atoms – the hydrogen atoms combine to form molecules of hydrogen gas Chloride ions lose electrons (oxidation) to form chlorine atoms – the chlorine atoms combine to form molecules of chlorine gas 2NaCl + 2H2O ? 2Na+ + 2OH- + Cl2 + H2

    14. Products These three products - hydrogen, chlorine and sodium hydroxide all have important uses in the chemical industry… Hydrogen: making ammonia; making margarine etc… Chlorine: killing bacteria in drinking water; killing bacteria in swimming pools; making bleach; making disinfectants; making hydrochloric acid; making PVC; making CFC's etc… Sodium hydroxide: making soap; making paper; making ceramics etc…

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