Unit 8 - Acids And Alkalis

Question 1

What pH are acids?

Answer 1

<7

Question 2

What is an ion?

Answer 2

An atom that has a charge through losing or gaining an electron

Question 3

What are polyatomic ions?

Answer 3

Formed when a small group of atoms, held together by covalent bonds, lose or gain electrons. E.g Cl^-

Question 4

What is an indicator?

Answer 4

A substance that changes colour depending on the pH

Question 5

What colour does litmus turn in acids and alkalis

Answer 5

Acid = red
Alkali = blue

Question 6

What colour does metal orange turn in acids and alkalis

Answer 6

Acids = red
Alkali = yellow

Question 7

What ions do acids produce excess of when dissolved in water?

Answer 7

H+

Question 8

What ion do alkalis produce excess of when dissolved in water?

Answer 8

(OH)-

Question 9

What is concentrated solution?

Answer 9

When the solution contains a lot of dissolved solute per unit volume

Question 10

What does it mean for an acid to have a high concentration?

Answer 10

There are more hydrogen ions in a certain volume so it is more acidic making the pH lower

Question 11

Describe the concentration of pure solutions

Answer 11

Low, equal concentrations of hydrogen and hydroxide ions

Question 12

What is the equation for concentration?

Answer 12

Concentration = amount dissolved/ volume of solution

Question 13

What are the units for concentration

Answer 13

g dm^-3

Question 14

What happens when the concentration of hydrogen ions increase by a factor of 10?

Answer 14

The pH decreases by 1

Question 15

If there is a pH of 0 and a pH of 4, what is the concentration difference from 0 to 4?

Answer 15

10 x 10 x 10 x 10 =10,000

Question 16

What does a strong acid mean? (2)

Answer 16

The molecules dissociate completely into ions when dissolved in water, produce high concentrations of hydrogen ions

Question 17

What is the difference between strong and weak acids?

Answer 17

Strong = fully dissociate producing more single hydrogen ions
Weak = partly dissociate meaning some hydrogen ions are still bonded, making it less acidic

Question 18

What do the chemical properties of an acid depends on?

Answer 18

The type of acid and the concentration

Question 19

What are bases

Answer 19

Substances that neutralise acids to form a salt and water only

Question 20

What types of metals are all bases

Answer 20

Metal oxides

Question 21

What are the 3 state symbols? (4)

Answer 21

Solid - (s)
Liquid - (l)
Gas - (g)
Dissolved in water - (aq)

Question 22

What happens to the ions during neutralisation

Answer 22

The hydrogen ions in the acid combine with oxide ions to form water. This removes the hydrogen ions and so the pH increases (more neutral)

Question 23

How are the salts formed in neutralisation?

Answer 23

The hydrogen ions in the acid are replaced with metal ions forming the soluble salt

Question 24

Hen preparing a salt, why is an excess amount of base always added

Answer 24

To ensure that all of the acid is used up

Question 25

What is crystallisation?

Answer 25

When the water is evaporated, leaving the salt

Question 26

Explain the core practical - preparing copper sulphate

Answer 26

Measure 20 cm^3 of dilute sulphuric acid Warm the liquid in a water bath Add copper oxide powder until it is in excess Filter the mixture and transfer the filtrate to an evaporating basin Heat the filtrate over a beaker of water over a Bunsen burner until crystals start to form Leave on the side for a few days for all the water to evaporate

Question 27

What is the word equation for neutralisation using a base

Answer 27

Base + acid —> salt + water

Question 28

What is an alkali?

Answer 28

A base that can dissolve in water

Question 29

What groups of hydroxide tend to be alkalis?

Answer 29

Group 1 and 2 hydroxides

Question 30

Why are there 2 hydroxide ions for group 2 metal hydroxides?

Answer 30

Group 2 have a charge of +2 so there needs to be 2 hydroxide ions to cancel the charge

Question 31

What is the word equation for an alkali to react with an acid

Answer 31

Alkali + acid —> salt + water

Question 32

How do you balance an equation

Answer 32

Make sure there is the same amount of each atom on each side, use large numbers at the start and don’t change the formula of a compound

Question 33

What acid is naturally found in stomachs

Answer 33

Hydrochloric acid

Question 34

Explain the core practical - investigating neutralisation

Answer 34

Add 50cm^3 of dilute hydrochloric acid to a beaker Calculate the pH using universal indicator on a white tile Measure 0.3g of calcium hydroxide onto a weighing boat Add this to the beaker and record the pH Repeat 7 times and draw a graph

Question 35

What type of reaction is when an alkali reacts with an acid to make a salt and water?

Answer 35

Neutralisation

Question 36

What type of ions do alkalis contain?

Answer 36

Hydroxide - OH-

Question 37

What happens with the ions in neutralisation involving an alkali?

Answer 37

The hydrogen ions from the acid react with the hydroxide ions form the alkali to form water The remaining ions bond to form the salt when the water evaporates

Question 38

For crystallisation, why is it important to have a neutral solution before evaporating the water

Answer 38

Otherwise you will contaminate the excess reactant with the salt

Question 39

What does titration allow you to do

Answer 39

To have a neutral solution for crystallisation

Question 40

Describe titration

Answer 40

Acid is added from a burette to a fixed volume of alkali, using a pipette, in a comical flask Indicator is added. Slowly add the acid drop by drop unit, the indicator changes colour Repeats to get more reliable results

Question 41

What is a burette

Answer 41

A tall piece of glassware with 0.1cm^3 graduations, it has a tap at the bottom to control the flow. Can add form by drop.

Question 42

What is the end-point of a neutralisation reaction

Answer 42

When the indicator changes colour

Question 43

After titration, how do you make a pure salt?

Answer 43

Using the known volume of acid needed, carry out iteration without the indicator

Question 44

What is the reaction for a metal and an acid

Answer 44

Meta + acid —> salt + hydrogen

Question 45

Which part of the reactivity series do the metals not react with dilute acids

Answer 45

The bottom end

Question 46

What is effervescence

Answer 46

Bubbles in a liquid e.g hydrogen given off in a solution

Question 47

In a metal + acid reaction, how is the name of the salt determined?

Answer 47

The metal first + the acid

Question 48

In a metal+ acid reaction, what happens to the ions

Answer 48

The metal atoms react with the hydrogen ions to form metal ions and hydrogen molecules. The other ions from the acid don’t change

Question 49

What are spectator ions?

Answer 49

Ions that don’t change in a reaction

Question 50

How do hydrogen ions form hydrogen molecules

Answer 50

By gaining electrons

Question 51

What does a half equation show?

Answer 51

How part of an equation forms a product e.g how hydrogen ions in an equation forms hydrogen molecules

Question 52

What is an oxidisation reaction?

Answer 52

A reaction where there is a loss of electrons

Question 53

What is a reduction reaction?

Answer 53

Where there is a gain in electrons

Question 54

What is the acronym to remember oxidisation and reduction reactions?

Answer 54

OILRIG

Question 55

What is the word equation for a metal carbonate and an acid reaction

Answer 55

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

Question 56

How do the ions in a CASHOCO reaction react?

Answer 56

The hydrogen ions from the acid react with the carbonate ions which form carbon dioxide and water.

Question 57

What do ionic equations not contain

Answer 57

Spectator ions

Question 58

What is a precipitation reaction?

Answer 58

A reaction which soluble substances in solutions cause an insoluble precipitate to form

Question 59

What salts are all soluble in water

Answer 59

Common Sodium, potassium and ammonium | Nitrates

Question 60

What 2 chlorides are insoluble in water

Answer 60

Silver and lead

Question 61

Which sulphate are insoluble in water (3)

Answer 61

Lead, barium, calcium

Question 62

What carbonates and hydroxides are soluble in water

Answer 62

Sodium, potassium, ammonium

Question 63

How are the products from a precipitation reaction determined

Answer 63

Switch the second part of the compounds

Question 64

How do you know which ions in a precipitate reaction are spectator ions

Answer 64

The ones that don’t change, e,g the state symbol

Question 65

What is the ionic equation for: | CuSO4 (aq) + K2 CO3 (aq) —> CuCO3 (s) + K2SO4 (aq)

Answer 65

Cu (aq) + CO3 (aq) —> CuCO3 (s)

Question 66

What are the reactants of a precipitate reaction?

Answer 66

2 soluble salts

Question 67

How can a dry insoluble salt be prepared from a precipitate reaction

Answer 67

Mix the soluble salts together in a beaker Filter the solution Pour distilled water over the precipitate Dry in warm oven