SC8 Acids and Alkalis

Question 1

What is a ph scale?

Answer 1

A scale used to determine how acidic or alkaline a solution is

Question 2

What number on the pH scale are considered acidic?

Answer 2

<7

Question 3

What number on the pH scale are considered alkaline?

Answer 3

> 7

Question 4

What number on the pH scale are considered neutral?

Answer 4

7

Question 5

How can we find out the pH of a substance?

Answer 5

Using an indicator

Question 6

Name a few common indicators

Answer 6

• litmus
• methyl orange
• phenolphthalein

Question 7

What colour is litmus in acidic solutions?

Answer 7

Red

Question 8

What colour is litmus in alkaline solutions?

Answer 8

Blue

Question 9

What colour is methyl orange in acidic solutions?

Answer 9

Red

Question 10

What colour is methyl orange in alkaline solutions?

Answer 10

Yellow

Question 11

What colour is phenolphthalein in acidic solutions?

Answer 11

colourless

Question 12

What colour is phenolphthalein in alkaline solutions?

Answer 12

Pink

Question 13

What happens when acids dissolve in water?

Answer 13

They produce an excess of hydrogen ions

Question 14

How does the concentration change in acidic solutions?

Answer 14

The higher the number of hydrogen ions in a certain volume, the higher the concentration. A higher concentration ensures a lower pH

Question 15

What makes a solution acidic?

Answer 15

It contains hydrogen ions

Question 16

What makes a solution alkaline?

Answer 16

The presence of hydroxide ions

Question 17

How does concentration change in alkaline solutions?

Answer 17

The more the concentration of hydroxide ions increases the pH of an alkaline solution

Question 18

What is the difference between a dilute and a concentrated solution?

Answer 18

• a dilute solution only contains a small amount of a dissolved solute
• a concentrated solution contains a large amount of a dissolved solute

Question 19

How is concentration calculated?

Answer 19

amount dissolved/volume of solution

Question 20

How is the concentration of hydrogen ions linked to the pH of an acid?

Answer 20

If the concentration of hydrogen ions is increased by a factor of 10, the pH decreases by 1

Question 21

What is a strong acid?

Answer 21

An acid wherein ions completely dissociate into the solution

Question 22

What is a weak acid?

Answer 22

An acid wherein ions only partially dissociate into the solution

Question 23

What are bases?

Answer 23

Substances that neutralise acids to form a salt and water only

Question 24

Write the word equation for when a metal oxide reacts with an acid

Answer 24

metal oxide + acid —> salt + water

Question 25

What happens during a neutralisation reaction?

Answer 25

The hydrogen ions from the acid react with the hydroxide ions in the alkali/ base forming water, which is neutral

Question 26

What is the difference between a base and an alkali?

Answer 26

An alkali is a soluble base, which means it can dissolve in water

Question 27

What are some examples of bases?

Answer 27

Metal oxides and metal hydroxides

Question 28

What happens in acid-metal reactions which results in the formation of a salt?

Answer 28

The salt is formed by replacing the hydrogen ions in acids with metal ions

Question 29

What salt does hydrochloric acid form?

Answer 29

Chloride

Question 30

What salt does sulfuric acid form?

Answer 30

Sulphate

Question 31

What salt does nitric acid form?

Answer 31

Nitrate

Question 32

State the word equation for a metal and an acid

Answer 32

metal + acid ---> salt + hydrogen

Question 33

State the word equation for an acid and a metal carbonate

Answer 33

metal carbonate + acid ---> salt + water + carbon dioxide

Question 34

State the word equation for a metal hydroxide and an acid

Answer 34

metal hydroxide + acid ---> salt + water

Question 35

What is a hazard associated with hydrochloric acid?

Answer 35

Concentrated acid is corrosive and can damage skin and clothes

Question 36

What is a hazard associated with calcium hydroxide powder?

Answer 36

- causes skin damage - causes eye irritation - may cause respiratory irritation

Question 37

How can we prevent a hazard occurring with hydrochloric acid?

Answer 37

Use dilute hydrochloric acid

Question 38

How can we prevent hazards from occurring in the lab?

Answer 38

- wear eye protection - wear gloves

Question 39

What is solubility?

Answer 39

A measure of the maximum mass that will dissolve in a given volume of solvent at a particular temperature

Question 40

What is a precipitate?

Answer 40

An insoluble product that forms when two solutions are mixed and reacted together

Question 41

Name some soluble ionic compounds

Answer 41

- all potassium, sodium and ammonium salts - all nitrates - most common chlorides - most common sulfates

Question 42

Name some soluble carbonates

Answer 42

- sodium carbonate - potassium carbonate - ammonium carbonate

Question 43

Name some soluble hydroxides

Answer 43

- sodium hydroxide - potassium hydroxide - ammonium hydroxide

Question 44

Name some insoluble ionic compounds

Answer 44

- most common hydroxides - most common carbonates

Question 45

Name some insoluble chlorides

Answer 45

- silver chloride - lead chloride

Question 46

Name some insoluble sulfates

Answer 46

- lead sulphate - calcium sulphate - barium sulphate

Question 47

What is the reaction that produces a precipitate?

Answer 47

Precipitate reaction

Question 48

How can the solubility rules be used to predict the formation of a precipitate?

Answer 48

If the products fall into the 'soluble' column, they will not form a precipitate and if they fall into the 'insoluble' column, they will form a precipitate

Question 49

What happens when a metal carbonate reacts with an acid?

Answer 49

- bubbles of carbon dioxide form - solid metal carbonate disappears if there is enough acid to react with all of it

Question 50

What is an oxidation reaction?

Answer 50

A loss of electrons

Question 51

What is a reduction reaction?

Answer 51

A gain in electrons

Question 52

Describe the test for hydrogen

Answer 52

Using a burning splint, hold it over a test tube filled with gas and it will produce a 'squeaky pop' sound

Question 53

Describe the test for carbon dioxide

Answer 53

Turns limewater milky when bubbled through