Chemical changes

Question 1

What are the 2 ways to measure the pH of a solution

Answer 1

• pH probe
• Chemical indicator

Question 2

Universal indicator

Answer 2

• acid = red
• alkaline = bluey-purple

Question 3

2 reasons why the pH probe is more reliable than indicator

Answer 3

• Determining the colour of the
  indicator is subjective
• produces more accurate results

Question 4

What is the ion responsible for making an alkaline pH when dissolved

Answer 4

OH-

Question 5

What is an acid?

Answer 5

any substance that forms an aqueous solution with a pH less than 7

Question 6

What ions do acids form?

Answer 6

H+ ions in water

Question 7

What is a base?

Answer 7

any substance with a pH greater than 7

Question 8

What is an alkali?

Answer 8

A base that dissolves in water to form a solution with a pH greater than 7

Question 9

What ions do alkalis form?

Answer 9

0H- in water

Question 10

Neutralization reaction

Answer 10

acids + base –> salt + water

Question 11

common acids

Answer 11

hydrochloric - HCL
sulfuric - H2SO4
nitric - HNO3

Question 12

common bases

Answer 12

sodium hydroxide - NaOH
calcium carbonate - CaCO3

Question 13

What are the 3 types of indicators?

Answer 13

• phenolphthalein
• litmus
• methyl orange

Question 14

Phenolphthalein

Answer 14

• acids - colourless
• alkalis = pink

Question 15

Litmus

Answer 15

• acid = red
• alkaline = blue

Question 16

Methyl orange

Answer 16

• acid = red
• alkaline = yellow

Question 17

What makes a strong acid?

Answer 17

Ionise completely in water
- all acid particles dissociate to release H+ ions

Question 18

ionise completely

Answer 18

all of the acid particles will dissociate
(reactants turn completely into products)

Question 19

examples of strong acids

Answer 19

• hydrochloric acid
• sulfuric acid
• nitric acid

Question 20

examples of weak acids

Answer 20

• ethanoic acid
• citric acid
• carbonic acid

Question 21

What makes a weak acid?

Answer 21

do not fully ionise in solution
- only small proportion of acid particles dissociate to release H+ ions

Question 22

Why are weak acids weak?

Answer 22

Ionisation of weak acid is a reversible reaction which sets up an equilibrium between the undissociate and dissociate acid.

Question 23

Strength of acids

Answer 23

How much an acid dissociates

Question 24

Concentration of acids

Answer 24

How much acid there is in a certain volume

Question 25

pH scale

Answer 25

A measure of the concentration of H+ ions in a solution

Question 26

Why does a strong acid have a lower pH than weak acids

Answer 26

Higher proportion of the strong acid particles will dissociate to release their hydrogen ions, which the concentration of those ions determine the pH

Question 27

The reactivity series

Answer 27

potassium sodium lithium calcium magnesium carbon zinc iron hydrogen copper

Question 28

What is the reactivity series for

Answer 28

How easily it forms positive ions

Question 29

How to make sure its a fair test when testing how reactive the metal is

Answer 29

- each of the metal sample has : - same mass/surface area - use the same type/ concentration of acid

Question 30

Metals + acid ---->

Answer 30

Salts + hydrogen

Question 31

Metals + water ---->

Answer 31

Metal hydroxide + hydrogen

Question 32

metal oxide + acid

Answer 32

salt + water

Question 33

oxidation

Answer 33

gaining of oxygen

Question 34

Reduction

Answer 34

loss of oxygen

Question 35

Oxidation in terms of electrons

Answer 35

loss of electrons

Question 36

Reduction in terms of electrons

Answer 36

Gaining of electrons

Question 37

Redox reaction

Answer 37

Where oxidation and reduction occurs at the same time