Chapter 5 - Acids, bases and salts

Question 1

What is an indicator ?

Answer 1

An indicator is one colour in acid and a different colour in alkali

Question 2

What colour is blue and red litmus paper in acids and alkalis

Answer 2

in acid in alkali in neutral

RED red blue red

BLUE red blue blue

Question 3

What colour does Phenolphthalein go in acid alkali and neutral solutions ?

Answer 3

acid : colourless
alkali : pink
neutral : colourless

Question 4

What colour does Methyl orange go in acid alkali and neutral solutions ?

Answer 4

acid : red
alkali : yellow
neutral : orange

Question 5

What is an acid ?

Answer 5

An acid is a substance that dissolves in water producing hydrogen ions (H+(aq))

Question 6

What negative ion does all 3 acids produce ?

Answer 6

hydrochloric acid (HCL) : chloride
sulfuric acid (H2SO4) : sulfate
nitric acid (HNO3) : nitrate

Question 7

What is an alkali ?

Answer 7

An alkali is a substance that dissolves n water producing hydroxide ions

Question 8

What classifies a strong acid ?

Answer 8

Strong acids completely ionise in water

Question 9

What classifies a weak acid ?

Answer 9

Weak acids are acids that are partially ionise in water

Question 10

What is a strong alkali ?

Answer 10

Strong alkalis are alkalis that are completely ionised in water

Question 11

What is a weak alkali ?

Answer 11

Weak alkalis are alkalis that are partially ionised in water

Question 12

Explain the pH scale

Answer 12

• pH 7 in neutral
• pH less than 7 is acidic
• pH more than 7 is alkaline

Question 13

What is the pH of a strong acid and give some examples

Answer 13

pH 0-2

examples : sulfuric acid, hydrochloric acid

Question 14

What is the pH of a weak acid and give some examples

Answer 14

pH 3-6

examples : ethanoic acid, carbonic acid

Question 15

What is the pH of a weak alkali and give some examples

Answer 15

pH 8-11

examples : ammonia

Question 16

What is the pH of a strong alkali and give some examples

Answer 16

pH 12-14

examples : sodium hydroxide and potassium hydroxide

Question 17

What is the pH of a neutral and give some examples

Answer 17

pH 7

examples : water

Question 18

What is a more accurate way of finding the pH ?

Answer 18

Use a pH meter, this will give the pH to one decimal place

Question 19

What is a concentrated acid ?

Answer 19

A concentrated acid contains a large number of acid particles dissolved per unit volume

Question 20

What is a dilute acid ?

Answer 20

A dilute acid contains a small number of acid particles dissolved per unit volume

Question 21

What does the hazard symbol corrosive look like, mean and give an example

Answer 21

Looks like : acid spilling over a hand and a work top
means : burns and destroys living tissues
examples : concentrated acid

Question 22

What does the hazard symbol explosive look like, mean and give an example

Answer 22

Looks like : an explosion
means : explodes if exposed to flame, heat or knocked
examples : potassium

Question 23

What does the hazard symbol flammable look like, mean and give an example

Answer 23

Looks like : a flame
means : catches fire easily when in contact with air
examples : ethanol

Question 24

What does the hazard symbol toxic look like, mean and give an example

Answer 24

Looks like : skull and crossbones
means : can kill by poisoning
examples : weed killer, cyanide

Question 25

What does the hazard symbol moderate hazard look like, mean and give an example

Answer 25

Looks like : an exclamation mark means : may be harmful or an irritant examples : dilute sodium hydroxide

Question 26

What is a salt ?

Answer 26

A salt is the compound formed when some or all of the hydrogen ions of an acid are replaced by metal or ammonium ions

Question 27

What are some general observations that can be made during an acid reaction ?

Answer 27

- bubbles - solid disappears and solution is produced - heat released

Question 28

What is the general equation when a metal reacts with an acid ?

Answer 28

metal + acid ---- > salt + hydrogen

Question 29

What is the test for hydrogen ?

Answer 29

- apply a lighted splint | - a popping sound results

Question 30

What is the general equation for an acid plus a base ?

Answer 30

base + acid ----> salt + water

Question 31

What is a base ?

Answer 31

A base is a metal oxide or metal hydroxide that neutralises an acid to produce a salt and a water

Question 32

What is an alkali ?

Answer 32

a soluble base

Question 33

What does the term neutralisation mean ?

Answer 33

Neuralisation is the reaction between the hydrogen ions in an acid and the hydroxide ions in an alkali to produce water

Question 34

What is the ionic equation for neutralisation ?

Answer 34

H+ (aq) + OH- (aq) ------> H20 (l)

Question 35

What is an exothermic reaction ?

Answer 35

An exothermic reaction is one which heat energy is given out.

Question 36

What is the general equation for a metal carbonate and an acid ?

Answer 36

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

Question 37

What is the test for carbon dioxide ?

Answer 37

- bubble the gas into colourless limewater | - the solution will turn milky if CO2 is present

Question 38

What is the equation for ammonia and an acid ?

Answer 38

ammonia + acid ----> ammonium salt

Question 39

What is the method of preparing metal, oxide and carbonate salts ?

Answer 39

add excess insoluble substance to the acid

Question 40

What is the method of preparing a hydroxide salts ?

Answer 40

add acid to alkali in the presence of an indicator

Question 41

How would you dry crystals ?

Answer 41

- between sheets of filter paper - in a low-temperature oven - in a desiccator