Int 2 Chemistry Unit 3 Acids, Bases + Metals

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1

pH below 7

Acidic

2

pH above 7

Alkaline

3

pH = 7

Neutral

4

pH pure water

Neutral pH = 7

5

Soluble non-metal oxides

acidic

6

Soluble metal oxides

alkaline

7

Soluble hydroxides

alkaline

8

Ammonia dissloves in water to produce

an alkali

9

Vinegar

Weak acid

10

Bleach

Strong alkali

11

Sodium hydroxide

strong alkali

12

Ammonium hydroxide

Weak alkali

13

Sulphuric acid

Strong acid

14

Hydrochloric acid

Strong acid

15

Acidic solution

contains more hydrogen ions than hydroxide ions.

16

Alkaline solution

contains more hydroxide ions than hydrogen ions.

17

In water and neutral solutions

concentration of hydrogen ions EQUALS concentration of hydroxide ions.

18

Diluting an acid:

pH rises towards 7
concentration of hydrogen ions decreases
concentration of hydroxide ions increases

19

Diluting an alkali

pH falls towards 7
concentration of hydroxide ions decreases
concentration of hydrogen ions increases

20

Water equilibrium:

Water molecules dissociate to form hydrogen ions and hydroxide ions. This is reversible.

21

When a reversible reaction is in equilibrium

concentrations of reactants and products are constant, but may be different from each other.

22

Moles (concentration)

moles = concentration x volume
volume must be in litres

23

In aqueous solution
strong acids

completely dissociate into ions

24

In aqueous solution
weak acids

partially dissociate into ions

25

In aqueous solution
strong bases

completely dissociate into ions

26

In aqueous solution
weak bases

partially dissociate into ions

27

Nitric acid

Strong acid

28

Ethanoic acid

Weak acid

29

Compared to a weak acid, a strong acid (of equal concentration) has

lower pH
higher conductivity
faster rate of reaction

30

Compared to a weak base, a strong base (of equal concentration) has

higher pH
higher conductivity
faster rate of reaction

31

Neutralisation

reaction of acids with bases
salt and water are always produced

32

Titration equation

Pa Ca Va = Pb Cb Vb
P = power - No. hydrogen or hyroxide ions
C = concentration, V = volume
a = acid, b = base

33

Examples of bases:

metal oxide
metal hydroxides
metal carbonates

34

Acid + metal hydroxide →

salt + water
hydrogen ions and hydroxide ions react to form water

35

Acid + metal oxide →

salt + water
hydrogen ions and oxide ions react to form water

36

Acid + metal carbonate →

salt + water + carbon dioxide
hydrogen ions and carbonate ions react to form water and carbon dioxide

37

Water soluble bases form

Alkalis

38

Everyday examples of neutralisation

treatment of acid indigestion
adding lime to acidic lochs and soil.

39

Acid + metal →

salt + hydrogen
only works with metals above hydrogen in the Electrochemical series (databook pg 7)

40

Test for hydrogen gas

hydrogen burns with a pop!

41

Acid rain caused by

sulphur dioxide (from burning fossil fuels) and nitrogen dioxide (from sparking air in car engines) dissolving in water in atmosphere.

42

Acid rain has damaging effects on:

buildings made from carbonate (marble) rock
structures made of iron and steel
soils and plant and animal life

43

A salt is:

compound in which the hydrogen ions of an acid have been replaced by metal ions (or ammonium ions).

44

Hydrochloric acid salts are

chlorides

45

Nitric acid salts are

nitrates

46

Sulphuric acid salts are

sulphates

47

Some salts containing nitrogen e.g. ammonium nitrate, ammonium sulphate and potassium nitrate are used as

fertilisers
These salts are soluble in water

48

Precipitation

reaction of two solutions to form a solid
insoluble salts can be prepared by precipitation
(use pg 5 of databk)

49

Spectator ions

do not take part in the reaction
their state and charge remains the same.

50

Electricity can be produced in a simple cell by

connecting two different metals with an electrolyte between them.

51

Electrochemical series

Series produced by measuring the voltage produced between different metal pairs.

52

Displacement

a metal is added to a solution containing ions of a metal lower in the electrochmical series.
higher metal forms ions in solution. Lower metal forms atoms (solid at bottom of beaker).

53

Position of hydrogen in the electrochemical series

is worked out by reacting different metals with acid.

54

Direction of electron flow in a cell

electrons flow through wires from metal higher up in the electrochemical series to the one lower down.

55

Ion bridge

allows the movement of IONS to complete the circuit.

56

Oxidation

loss of electrons

57

Reduction

gain of electrons

58

Redox

oxidation and reduction occur together

59

metal ion → metal atom

reduction

60

metal atom → metal ion

oxidation

61

ion-electron equations

used to show oxidation and reduction
find them pg 7 of databooklet.

62

Metal + water →

metal hydroxide + hydrogen
only magnesium and above will react

63

Metal + oxygen →

metal oxide
only copper and above will react

64

Metal ore

naturally occuring metal compound

65

Metals found uncombined in Earth crust are

less reactive.
Gold, silver, copper

66

Blast Furnace

used to extract iron from iron ore

67

Blast furnace key reactions:

C + O2 → CO2
CO2 + C → CO
Fe2O3 + CO→ Fe + CO2 (these equations must be balanced)

68

Aluminium and other reactive metals are extracted from ores using

electrolysis

69

Corrosion

chemical reaction which involves the surface of a metal changing from an element to compound.

70

Rusting

corrosion of iron

71

Substances needed for rusting are

water and oxygen

72

Stages in rusting are:

1) iron atoms lose 2 e- to form iron (II) ions
2) Iron (II) ions lose 1 e- to form iron (III) ions
e- lost by iron go to water and oxygen to form hydroxide ions

73

Ferroxyl indicator turns blue in presence of

iron (II) ions

74

Ferroxyl indicator turns pink in presence of

hydroxide ions

75

Rate of corrosion increased by

acid rain
salt
attaching metal lower in electrochemical series (unless iron surface is completely covered)

76

Corrosion stopped by

Physical protection - painting etc
Sacrificial protection
Connecting iron to negative terminal of battery

77

Physical protection

barrier to water and oxygen
painting, greasing, electroplating, galvanising, tin-plating, coating with plastic

78

Sacrificial protection

Fe attached to metal higher in E.C.S.
e- flow from higher metal to Fe. Other metal corrodes in place of Fe.