Chemical Changes

Question 1

OIL RIG MEANING

Answer 1

Oxidation is lost Reduction is gain

Question 2

Metal + Water →

Answer 2

Metal Hydroxide + Hydrogen

e.g. Calcium + Water → Calcium hydroxide + Hydrogen

Question 2

Metal + Acid →

Answer 2

Salt + Hydrogen

e.g. Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen

Question 3

Very reactive metals in the series

Answer 3

Potassium, Sodium, Lithium, Calcium: react with cold water + acids violently

Question 4

Fairly reactive metals in the reactivity series

Answer 4

Magnesium, Aluminium, Zinc, Iron: react with acids, but not with cold water

Question 5

Low reactivity metals in the reactivity series

Answer 5

Copper, Silver, Gold: don’t react with water or dilute acids —

Question 6

how are very reactive metals extracted?

Answer 6

Very reactive metals (like potassium, sodium, calcium) are extracted by electrolysis.

Question 6

How are less reactive metals extracted?

Answer 6

Less reactive metals (like iron, zinc) are extracted by reduction with carbon.

Question 7

How are unreactive metals extracted?

Answer 7

Unreactive metals (like gold, silver) are found native — don’t need extracting from compounds.

Question 8

Oxidation and reduction in terms of electrons

Answer 8

Oxidation = gain of oxygen

Reduction = loss of oxygen

Question 9

A more reactive metal displaces….

Answer 9

A more reactive metal displaces a less reactive one from its compound.

Example:
Magnesium + Iron oxide → Magnesium oxide + Iron

Reactions with Water and Acids:

Question 10

Describe what you would observe when magnesium is added to dilute hydrochloric acid.

Answer 10

Effervescence / fizzing / bubbles of gas

Magnesium dissolves / disappears

Question 11

Copper does not react with hydrochloric acid. Explain why, using the reactivity series.

Answer 11

Copper is less reactive than hydrogen.

A metal must be more reactive than hydrogen to displace it from acid.

Copper cannot displace hydrogen from hydrochloric acid.

So no reaction takes place.

Question 12

Magnesium reacts with copper sulfate solution. Write the word equation and explain why this is a displacement reaction.

Answer 12

Explanation:

Magnesium is more reactive than copper.

It displaces copper from its compound.

Magnesium takes the place of copper in copper sulfate.

Copper is left as a solid metal.

Question 13

Name a metal that is found in the Earth’s crust as a pure element and explain why.

Answer 13

Gold, because it is very unreactive.
It does not form compounds easily, so it’s found as a native metal.

Question 14

Metal + Acid →

Answer 14

Salt + Hydrogen gas
Example:
Mg + 2HCl → MgCl₂ + H₂