Chemical Changes

Question 1

How are metal oxides produced?

Answer 1

Metals react with oxygen to produce metal oxides. The reactions are oxidation reactions because the metals gain oxygen.

Question 2

What is reduction in terms of oxygen.

Answer 2

reduction is the loss of oxygen

Question 3

What is oxidisation in terms of oxygen?

Answer 3

the gain of oxygen

Question 4

How are positive ions formed?

Answer 4

When metals react with other substances the metal atoms form positive ions. They are formed through the loss of electrons

Question 5

What is the reactivity of a metal related to ?

Answer 5

The reactivity of a metal is related to its tendency to
form positive ions

Question 6

What is the reactivity series?

Answer 6

Metals can be arranged in order of their reactivity
in a reactivity series.

Question 7

What is the order of reactivity from most reactive to least?

Answer 7

Potassium , sodium, Lithium, Calcium, Magnesium, Carbon, Zinc , Iron, Hydrogen, Copper, Gold

Question 8

What is displacement?

Answer 8

A more reactive metal can displace a less reactive metal from a compound

Question 9

How can metals less reactive than carbon be extracted?

Answer 9

Metals less reactive than carbon can be extracted from their oxides by reduction with carbon.
Reduction involves the loss of oxygen

Question 10

What is oxidation in terms of electrons?

Answer 10

Oxidation is the loss of electrons and reduction is the gain of electrons.

Question 11

What do acids produce when reacted with some metals?

Answer 11

they produce salts and hydrogen

Question 12

How are acids neutralised?

Answer 12

Acids are neutralised by alkalis (eg soluble metal hydroxides) and bases (eg insoluble metal hydroxides and metal oxides) to produce
salts and water, and by metal carbonates to produce salts, water and carbon dioxide.

Question 13

What does the salt produced in any reaction between an acid and a base or alkali depend on?

Answer 13

• the acid used (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulfuric acid produces sulfates)
• the positive ions in the base, alkali or carbonate.

Question 14

How can soluble salts be made from acids?

Answer 14

Soluble salts can be made from acids by reacting them with solid insoluble substances, such as metals, metal oxides, hydroxides or
carbonates. The solid is added to the acid until no more reacts and the excess solid is filtered off to produce a solution of the salt.

Question 15

How can salt solutions be made into solid salts?

Answer 15

Salt solutions can be crystallised to produce solid salts.

Question 16

What ions to acid produce in aqueous solutions?

Answer 16

Acids produce hydrogen ions (H+ ) in aqueous solutions.

Question 17

What ions do alkali aqueous solutions contain?

Answer 17

Aqueous solutions of alkalis contain hydroxide ions (OH–).

Question 18

How can acid and alkali’s be measured?

Answer 18

using universal indicator

Question 19

What do aqueous solutions of acids have a ph of?

Answer 19

Aqueous solutions of acids have pH values of less than 7

Question 20

What do aqueous solutions of alkalis have a ph of?

Answer 20

aqueous solutions of alkalis have pH values greater than 7.

Question 21

What happens when there is neutralisation between an acid and an alkali?

Answer 21

In neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water

Question 22

What is a strong acid?

Answer 22

A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.

Question 23

What is a weak acid?

Answer 23

A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids

Question 24

Explain the process of Electrolysis

Answer 24

When an ionic compound is melted or dissolved in water, the ions are free to move about within the liquid or solution. These liquids
and solutions are able to conduct electricity and are called electrolytes.

Passing an electric current through electrolytes causes the ions to move to the electrodes. Positively charged ions move to the
negative electrode (the cathode), and negatively charged ions move to the positive electrode (the anode). Ions are discharged at the electrodes producing elements. This process is called electrolysis.

Question 25

What happens when a simple ionic compound is electrolysed in molten state using electrodes?

Answer 25

When a simple ionic compound (eg lead bromide) is electrolysed in the molten state using inert electrodes, the metal (lead) is produced
at the cathode and the non-metal (bromine) is produced at the anode.

Question 26

What happens in Electrolysis of aqueous solutions?

Answer 26

The ions discharged when an aqueous solution is electrolysed using inert electrodes depend on the relative reactivity of the
elements involved.

At the negative electrode (cathode), hydrogen is produced if the metal is more reactive than hydrogen.

At the positive electrode (anode), oxygen is produced unless the solution contains halide ions when the halogen is produced.

This happens because in the aqueous solution water molecules break down producing hydrogen ions and hydroxide ions that are
discharged.

Question 27

During electrolysis, at the cathode (negative electrode), positively charged ions gain electrons and so the reactions are reductions.

At the anode (positive electrode), negatively charged ions lose
electrons and so the reactions are oxidations.