Electrolysis

Last lesson we saw that certain atoms can gain or lose electrons to turn them into ions. The ions are affected by the electrodes of a power supply. Remember, opposites attract .... Some ions are attracted to the negative electrode (or cathode) so these are called positive ions. These positive ions will be pushed away from (repelled) the positive electrode (or anode). There are also negative ions that will be attracted to the positive electrode (anode) and they will be repelled by the negative electrode (cathode).

 

Fill in these missing words ...

When an atom gains or loses an it is called an ion. These ions can be either positive or . If you put two electrodes in a solution of positive and negative ions then the ions will move.

We know that opposites . So, positive ions will move to the electrode and ions will move to the positive electrode.

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Electrolysis of Salt Water (brine)

Electrolysis means using an electric current to seperate a mixture of ions. The chemical name for salty water is sodium chloride solution. In the seas and oceans there is plenty of salty water. Sodium chloride solution is made up of four different ions:

• Na⁺ (sodium)
• H⁺ (hydrogen)
• Cl^- (chlorine)
• OH^- (hydroxyl)

The hydrogen and chlorine ions collect together to form hydrogen gas and chlorine gas. The hydrogen ions go to the negative electrode (cathode) and the chlorine ions go to the positive electrode (anode).

So, from just sea water, scientists can use electrolysis to make hydrogen gas, chlorine gas, and a solution of sodium hydroxide.

Now answer these questions:

1. When an atom loses or gains an electron it is called a what ? iron onion ion sodium
2. Another name for the positive electrode is what ? anode anion cathode cation
3. Another name for the negative electrode is what ? anode anion cathode cation
4. Negative ions are attracted to which electrode ? negative positive neither both
5. Positive ions are attracted to which electrode ? negative positive neither both
6. What is the proper name for salty water ? sodium solution sodium hydroxide solution sodium chloride solution chlorine gas
7. What two gases are produced in the hydrolysis of sea water ? helium and hydrogen oxygen and chlorine oxygen and helium hydrogen and chlorine
8. What solution is left over after the electrolysis of sea water ? sodium solution sodium hydroxide solution sodium chloride solution chlorine gas
9. What is the other name for a positive ion ? onion cation anion caution
10. What is the other name for a negative ion ? onion cation anion caution

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Important words to remember Cathode the negative electrode Anode the positive electrode Anion a negative ion Cation a positive ion If you have trouble remembering these ... just remember that cations are pussytive !

 

Now fill in these missing words ...

The positive electrode is also called the , the cathode is another name for the electrode. Because we know that opposites we can work out that the positive ions (or cations) will go to the cathode and the negative ions (or ) will go to the .

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