Chemical Changes

Question 1

chlorine + sodium bromide

Answer 1

sodium chloride + bromine

Question 2

chlorine + sodium iodide

Answer 2

sodium chloride + iodine

Question 3

aluminium sulfate + magnesium

Answer 3

magnesium sulfate + aluminium

Question 4

calcium chloride + sodium

Answer 4

sodium chloride + calcium

Question 5

platinum sulfate + gold

Answer 5

gold sulfate + platinum

Question 6

zinc sulfate + magnesium

Answer 6

magnesium sulfate + zinc

Question 7

zinc + copper sulfate

Answer 7

zinc sulfate + copper

Question 8

Which is more reactive, zinc or lead?

Answer 8

zinc.

Question 9

Which is more reactive, sodium or aluminium?

Answer 9

sodium.

Question 10

Which is more reactive, magnesium or calcium?

Answer 10

calcium.

Question 11

In terms of reactivity, which metal displaces which?

Answer 11

A more reactive metal displaces a less reactive metal.

Question 12

How are unreactive metals extracted? Give an example.

Answer 12

Unreactive metals, such as gold, can be separated by physical methods.

Question 13

How can metal be extracted from compounds?

Answer 13

Using a more reactive metal.

Question 14

How can metals which are less reactive than carbon be extracted?

Answer 14

By heating them with carbon. A reduction reaction takes place as the carbon removes the oxygen from the oxide.

Question 15

How can metals which are more reactive than carbon be extracted?

Answer 15

By electrolysis of the molten metal compound.

Question 16

How can salts be produced from a metal?

Answer 16

By reacting it with an acid.

Question 17

What is the overall charge of salts? Why is this?

Answer 17

The overall charge of salts is zero, as the metal ions are positive, and the ions from the acid are negative.

Question 18

What is the formula for magnesium nitrate?

Mg2+ and NO3-

Answer 18

• Mg is 2+
• NO3 is 1-
• The ratio is 2:1.
• So, there must be two NO3.

The formula is: Mg(NO3)2

Question 19

How are copper sulfate crystals made from copper oxide?

Answer 19

• Add the copper oxide (in excess) to sulfuric acid, forming copper sulfate and water.
• Filter the solution to remove excess copper oxide.
• Evaporate some of the water with a bunsen burner.
• Leave the rest to evaporate slowly on a window seal.

Question 20

What two other ways can salts be obtained by?

Answer 20

• Neutralisation (acid and alkali).

- Reacting a carbonate with an acid.

Question 21

What ions are produced when acids are added to water?

Answer 21

Hydrogen ions (H+).

Question 22

What are bases?

Answer 22

Bases are compounds that react with acids and neutralise them, for example, metal oxides and metal hydroxides.

Question 23

What are alkalis?

Answer 23

Alkalis are bases that dissolve in water to make alkaline solutions. They are soluble hydroxides and produce hydroxide ions (OH-) in the solution.

Question 24

What are strong acids?

Answer 24

Acids that ionise completely in aqueous solutions.

Question 25

What are weak acids?

Answer 25

Acids that do not completely ionise.

Question 26

What is the relationship between concentration and pH of H+ ions?

Answer 26

As the concentration decreases, the pH of the solution increases. As the concentration increases by a factor of 10, the pH value decreases by one unit.