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Chemistry > Unit 8 - Acids And Alkalis > Flashcards

Unit 8 - Acids And Alkalis Flashcards

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1
Q

What pH are acids?

A

<7

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2
Q

What is an ion?

A

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

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3
Q

What are polyatomic ions?

A

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

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4
Q

What is an indicator?

A

A substance that changes colour depending on the pH

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5
Q

What colour does litmus turn in acids and alkalis

A 
Acid = red
Alkali = blue
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6
Q

What colour does metal orange turn in acids and alkalis

A 
Acids = red
Alkali = yellow
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7
Q

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

A

H+

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8
Q

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

A

(OH)-

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9
Q

What is concentrated solution?

A

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

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10
Q

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

A

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

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11
Q

Describe the concentration of pure solutions

A

Low, equal concentrations of hydrogen and hydroxide ions

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12
Q

What is the equation for concentration?

A

Concentration = amount dissolved/ volume of solution

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13
Q

What are the units for concentration

A

g dm^-3

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14
Q

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

A

The pH decreases by 1

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15
Q

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

A

10 x 10 x 10 x 10 =10,000

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16
Q

What does a strong acid mean? (2)

A

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

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17
Q

What is the difference between strong and weak acids?

A 
Strong = fully dissociate producing more single hydrogen ions
Weak = partly dissociate meaning some hydrogen ions are still bonded, making it less acidic
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18
Q

What do the chemical properties of an acid depends on?

A

The type of acid and the concentration

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19
Q

What are bases

A

Substances that neutralise acids to form a salt and water only

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20
Q

What types of metals are all bases

A

Metal oxides

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21
Q

What are the 3 state symbols? (4)

A

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

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22
Q

What happens to the ions during neutralisation

A

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)

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23
Q

How are the salts formed in neutralisation?

A

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

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24
Q

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

A

To ensure that all of the acid is used up

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25
Q

What is crystallisation?

A

When the water is evaporated, leaving the salt

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26
Q

Explain the core practical - preparing copper sulphate

A

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

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27
Q

What is the word equation for neutralisation using a base

A

Base + acid —> salt + water

28
Q

What is an alkali?

A

A base that can dissolve in water

29
Q

What groups of hydroxide tend to be alkalis?

A

Group 1 and 2 hydroxides

30
Q

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

A

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

31
Q

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

A

Alkali + acid —> salt + water

32
Q

How do you balance an equation

A

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

33
Q

What acid is naturally found in stomachs

A

Hydrochloric acid

34
Q

Explain the core practical - investigating neutralisation

A

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

35
Q

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

A

Neutralisation

36
Q

What type of ions do alkalis contain?

A

Hydroxide - OH-

37
Q

What happens with the ions in neutralisation involving an alkali?

A

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

38
Q

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

A

Otherwise you will contaminate the excess reactant with the salt

39
Q

What does titration allow you to do

A

To have a neutral solution for crystallisation

40
Q

Describe titration

A

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

41
Q

What is a burette

A

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.

42
Q

What is the end-point of a neutralisation reaction

A

When the indicator changes colour

43
Q

After titration, how do you make a pure salt?

A

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

44
Q

What is the reaction for a metal and an acid

A

Meta + acid —> salt + hydrogen

45
Q

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

A

The bottom end

46
Q

What is effervescence

A

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

47
Q

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

A

The metal first + the acid

48
Q

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

A

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

49
Q

What are spectator ions?

A

Ions that don’t change in a reaction

50
Q

How do hydrogen ions form hydrogen molecules

A

By gaining electrons

51
Q

What does a half equation show?

A

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

52
Q

What is an oxidisation reaction?

A

A reaction where there is a loss of electrons

53
Q

What is a reduction reaction?

A

Where there is a gain in electrons

54
Q

What is the acronym to remember oxidisation and reduction reactions?

A

OILRIG

55
Q

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

A

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

56
Q

How do the ions in a CASHOCO reaction react?

A

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

57
Q

What do ionic equations not contain

A

Spectator ions

58
Q

What is a precipitation reaction?

A

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

59
Q

What salts are all soluble in water

A

Common Sodium, potassium and ammonium

Nitrates

60
Q

What 2 chlorides are insoluble in water

A

Silver and lead

61
Q

Which sulphate are insoluble in water (3)

A

Lead, barium, calcium

62
Q

What carbonates and hydroxides are soluble in water

A

Sodium, potassium, ammonium

63
Q

How are the products from a precipitation reaction determined

A

Switch the second part of the compounds

64
Q

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

A

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

65
Q

What is the ionic equation for:

CuSO4 (aq) + K2 CO3 (aq) —> CuCO3 (s) + K2SO4 (aq)

A

Cu (aq) + CO3 (aq) —> CuCO3 (s)

66
Q

What are the reactants of a precipitate reaction?

A

2 soluble salts

67
Q

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

A

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

Chemistry (12 decks)

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