C4-Chemical Changes KW

Question 1

Acid

Answer 1

Acids produce hydrogen ions (H+) in aqueous solutions. They have a pH range of 0-6.

Question 2

Alkali

Answer 2

Alkalis produce hydroxide ions (OH-) in aqueous solutions. They have a pH range of 8-14

Question 3

Electrolysis

Answer 3

The splitting up of an ionic compound using electricity. The electric current is passed through a substance causing chemical reactions at the electrodes and the decomposition of the materials

Question 4

Electrolyte

Answer 4

A solution containing free ions from the molten or dissolved ionic substance. The ions are free to move to carry charge

Question 5

Extraction

Answer 5

Extraction techniques are used to separate a desired substance when it is mixed with others

Question 6

Oxidation

Answer 6

A reaction involving the gain of oxygen (Oxidation is the loss of electrons (H))

Question 6

Negative electrode (cathode)

Answer 6

The electrode where hydrogen is produced if the metal in the electrolyte is more reactive than hydrogen. (It is where positively charged ions gain electrons and so the reactions are reductions (H))

Question 7

Neutralisation

Answer 7

The reaction when an acid and a base react to form water and a salt

Question 8

pH scale

Answer 8

The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution, and can be measured using universal indicator or a pH probe

Question 9

Positive electrode (anode)

Answer 9

The electrode where oxygen is produced unless the solution contains halide ions then the halogen is produced (It is where negatively charged ions lose electrons and so the reactions are oxidations (H))

Question 10

Redox reaction

Answer 10

A reaction in which both oxidation and reduction occur simultaneously

Question 11

Reduction

Answer 11

A reaction involving the loss of oxygen (Reduction is the gain of electrons (H))

Question 12

Reduction with carbon

Answer 12

Metals less reactive than carbon can be extracted from their oxides by reduction with carbon

Question 13

The reactivity series

Answer 13

Metals are arranged in order of their reactivity in a reactivity series. This can be used to predict products from reactions

Question 14

Strong acid (H)

Answer 14

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

Question 15

Titration

Answer 15

A technique used where a solution of known concentration is used to determine the concentration of an unknown solution

Question 16

Universal indicator

Answer 16

A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis

Question 17

Weak acid (H)

Answer 17

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