Rusting

Question 1

What is rust? (In terms of iron)

Answer 1

Hydrated iron(iii) oxide

Question 2

Explain why I am in rusts when exposed oxygen and water(4)

Answer 2

– Look at the half equations for Fe2+ ions and H2O then write the overall equation

– Fe2+ ions and OH^- ions produced combine to form a precipitate of iron (I I) Hydroxide

-The iron(ii) Hydroxide is further oxidised to iron(iii) oxide by oxygen

– Gradually iron(iii) hydroxide gradually turns into hydrated iron(iii) hydroxide

Question 3

Explain why rust is less likely to form an alkaline conditions(3)

Answer 3

Equilibrium of the half reaction between water and oxygen moves left to get rid of extra hydroxide ions

Equilibrium of iron half equation is pushed right to get rid of extra electrons

Therefore less Fe2+ ions take part in the reaction which means less rust

Question 4

What are the two main ways of preventing rust and explain (3)

Answer 4

– Adding a barrier to keep oxygen or water out for example coating with a polymer or oiling

– Placing a more reactive metal with the iron

– because it becomes oxidised instead of iron

Question 5

How does placing a more reactive metal on iron prevent rusting?

Answer 5

The metal which has a more negative E value will be oxidised in preference to iron

Question 6

What term is used to describe adding a coating of sink to an object?

Answer 6

Galvanising

Question 7

State the two substances that react with Iron to produce rust

Answer 7

Water and oxygen