C2: Electrolysis

Here are a set of revision cards for students taking AQA Addditional Science. These cards are based on electrolysis from the C2 (Chemistry) section. I hope these help you to revise! Please rate and comment on how to improve :) Also, I ahve a study gorup called AQA Additional Science where we discuss topics such as this one and many more form the Additional Science syllabus. Feel free to become a member, the more the merrier!

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  • Created by: I P B
  • Created on: 21-12-09 13:57

State Symbols

For electrolysis, you must know the 4 state symbols:

(s) = solid

(l) = liquid

(g) = gas

(aq) = aqueous solution

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Electrolysis

When an ionic substance is melted or dissolved in water, the ions are free to move about within the liquid or solution

electrolysis = passing an electric current through ionic substances that are molten or in solution to break them down into elements

During electrolysis, atoms become ions

The positively charged ions move to the negative electrode(Cathode)

The negatively charged ions move to the positive electrode (Anode)

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Electrolysis Continued...

For the atoms to become ions, electrons are either lost (oxidation) or gained (reduction) by the atoms. For you to remember this just use OIL RIG:

O = oxidation

I = is

L = loss (of electrons)

R = reduction

I = is

G = gain (of electrons)

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Purifying Copper

1. The electrodes are made of copper. The impure copper is at the anode (positive electrode) and the pure copper is at the cathode (negative electrode).

2. The copper ions (Cu2+) move from the electrolyte to the cathode (negative electrode) where they then gain 2 electrons (reduction) to form copper.

3. The copper atoms in the impure copper at the anode (positive electrode) lose two electrons (oxidation) to form copper ions (Cu2+). These electrons dissolve in the electrolyte.

4. As the copper ions are released at the positive electrode (anode) the impurities are set free and collect at the bottom.

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Purifying Copper Continued...

The reaction at each electrode can be shown using half equations

At the negative electrode (cathode):

Cu2 (aq) + 2e- > Cu (s) (reduction)

At the positive electrode (anode):

Cu (s) > Cu2 (aq) + 2e- (oxidation)

This shows that the purification of copper is a redox reaction as both oxidation and reduction have happened in the same reaction

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Electrolysing Brine (Sodium Chloride Solution)

1. The electrolyte is the Sodium Chloride Solution (Brine). The negative chloride ions (Cl-) form the electrolyte are attracted to the positive electrode (anode) Here, each Cl- loses an electron to form Cl atoms (oxidation), which then form molecules of Chlorine gas (Cl2).

2. At the cathode (negative electrode) the H+ ions gain electrons to make Hydrogen atoms (reduction) which then form hydrogen molecules (H2).

3. Na+ and OH- ions are left behind, which form a solution of sodium hydroxide (NaOH)

4. The products produced are chlorine gas, hydrogen gas and sodium hydroxide

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Electrolysing Brine (Sodium Chloride Solution) Con

The half equations for the electrolysis of brine (sodium chloride solution) are:

At the positive electrode (anode):

2Cl- (aq) > Cl2 (g) + 2e (reduction)

At the negative electrode (cathode):

2H+ (aq) + 2e > H2 (g) (oxidation)

This shows that the electrolysis of brine (sodium chloride solution) is a redox reaction as both oxidation and reduction occured in the smae reaction

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Products - From Electrolysing Brine

Hydrogen:

  • used in the maufacture of margarine
  • used to produce hydrochloric acid which is used in cleaning materials, manufacturing food and medicine as well as cosmetics

Chlorine:

  • used in water and sewage treatment
  • used in the maufacture of textiles and solvents, drugs to treat heart disease, leukaemia and arthiritis
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Products - From Electrolysing Brine Continued...

Sodium hydroxide:

  • purifies petroleum and matural gas
  • degreases metals
  • water and sewage treatment
  • used to manufacture paper, aluminium and soaps/detergents
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Comments

leah richards

it was great! just what i needed

thnx

Diamanti

it was electrolysis

..[z]α[я]α..

thanx, i actually understand it now x

Angharad

Thank you so much! These notes were extremely useful and easy to understand and remember! 

Nearly Einstein

This is really good. You have helped my revsion a lot! :)

Libby McGeough

thankyou so much, they really helped. :)

^^GhOsTy^^ XD

WHOAA !!!!! .... thnx ;)

bex

what does your name mean.....I understand it must be an acronym, but even so, I cannot work out what it means??? If it is not an acronym, I will pray for you babe

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