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Chemistry > November Test - chemical changes > Flashcards

November Test - chemical changes Flashcards

acids and bases topic electrolysis topic

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1
Q

what are metals

A

giant structures of atoms arranged in a regular pattern. the metal ions are arranged in regular layers on top of one another

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2
Q

why do metals have a strong boiling/melting point

A

strong electrostatic forces between negative delocalised electrons and positive metal ions, which require large amounts of energy to overcome

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3
Q

why are metals good conductors of electricity / thermal energy

A

delocalised electrons which are free to move and carry charge through the structure

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4
Q

why are metals malleable and ductile

A

metal atoms are equal in size and are arranged in rows which can slide over eachother

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5
Q

properties of metals

A
  • high boiling and melting points
  • malleable and ductile
  • good conductors of electricity and thermal energy
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6
Q

factors affecting the strength of metallic bonding

A
  • number of protons
  • number of electrons
  • size of ion
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7
Q

how does the number of delocalised electrons affect strength of metallic bonding

A

the higher number of delocalised electrons, the stronger the bond

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8
Q

how does the number of protons affect the strength of metallic bonding

A

the higher the number of protons, the stronger the strength of the metallic bond is

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9
Q

how does the size of the metal ion affect the strength of the metallic bond

A

the smaller the ion, the stronger the bond

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10
Q

why are alloys stronger and harder than pure metals

A

the regular arrangement of atoms are distorted and they cannot slide over eachother.

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11
Q

what is an alloy

A

a mixture of a metal and at least one other element.
The element distorts the regular arrangement of metals, so the layers cannot slide over eachother

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12
Q

what are alloys useful as

A

building/construction materials

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13
Q

examples of alloys

A

bronze, steel, brass

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14
Q

which elements react with cold water to produce bubbles of hydrogen gas

A

Potassium, Sodium and Calcium

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15
Q

most important metals in the reactivity series

A

Potassium, sodium, calcium, magnesium, aluminium, zinc, iron, tin, copper

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16
Q

the more reactive a metal is…

A

the faster the reaction will be
Hydrogen gas bubbles will be produced quicker

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17
Q

what is oxidation in terms of metals

A

when a metal atom gains oxygen

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18
Q

word equation for oxidation of metals

A

metal + oxygen -> metal oxide

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19
Q

what happens in displacement reactions

A

the more reactive metal displaces the less reactive metal in a compound.
EG: copper sulfate + magnesium -> magnesium sulfate + copper. because magnesium is more reactive than copper

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20
Q

how are most metals found

A

most metals found in the earth are combined with other elements to form compounds

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21
Q

two ways of extracting metals from a compound

A
  • reduction
  • electrolysis
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22
Q

which metals are extracted by reduction from a compound

A

metals which are less reactive than carbon can be extracted from their oxides by reduction with carbon
EG: Iron (III) oxide + CO -> Iron + CO2

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23
Q

definition of reduction in oxygen terms

A

reduction can be defined as a loss of oxygen

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24
Q

which metals are extracted by electrolysis or displacement reactions

A

metals which are MORE reactive than carbon can be extracted by electrolysis or displacement reactions

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25
Q

what is oxidation in terns of electrons

A

Oxidation is the loss of electrons

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26
Q

what is reduction in terms of electrons

A

reduction is the gain of electrons

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27
Q

oxidation of Zinc

A

Zn -> Zn2+ + 2e-

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28
Q

reduction of zinc

A

Zn2+ + 2e- -> Zn

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29
Q

which elements wont react with acids

A

Copper, Silver, Gold

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30
Q

which metals react with acids by producing bubbles of H2 gas

A

potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, copper, tin, lead

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31
Q

equation of reactions of acids with metals

A

acid + metal -> salt + hydrogen

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32
Q

word equation for magnesium reacting with sulfuric acid

A

Magnesium + Sulfuric acid -> Magnesium sulfate + hydrogen

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33
Q

what are reactions of acids with metals known as

A

redox reactions
- reduction and oxidation reactions

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34
Q

Half equations for magnesium reacting with sulfuric acid

A

Mg -> Mg2+ + 2e-
2H+ + 2e- -> H2

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35
Q

neutralisation reaction word equation

A

base + acid -> salt + water

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36
Q

how can acids be neutralised?

A

by adding a base or a carbonate

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37
Q

products of reacting an acid with a carbonate

A

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

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38
Q

word equation for neutralisation of copper oxide with sulfuric acid

A

copper oxide + sulfuric acid -> copper sulfate + water

39
Q

word equation for neutralisation of copper carbonate with Hydrochloric acid

A

Copper carbonate + Hydrochloric acid -> copper chloride + water + carbon dioxide

40
Q

how can soluble salts be made

A

by reacting acids with solid, insoluble substances such as metals, metal oxides, hydroxides or carbonates.
The solid is added to the heated acid until it is in excess. then its filtered, to produce a solution of the salt. salt solution is crystalised to produce solid salts

41
Q

Method of making soluble salt with HCL and Copper oxide

A

1) Add 40cm cubed of HCl to a beaker and heat it for 30s
2) Add in a spatula of copper oxide and stir with glass rod
3) keep adding spatulas of copper oxide until it is in excess
4) pour the contents in the beaker through filter paper in a funnel which is on top of a conical flask
5) Wait until all CuCl2 has been filtered through
6) Pour copper chloride solution into an evaporating basin and heat it over boiling water
7) stop heating until crystals begin to form on the edges and let it sit to the side
8) once crystals have formed fully, dry them on filter paper

42
Q

why do we use filter paper to dry the crystals, rather than place them in an oven to heat it dry

A

to avoid removing water of crystallisation and white anhydrous copper sulphate crystals could form

43
Q

what are acids

A

substances which produce H+ ions in aqueous solutions

44
Q

what do aqueous solutions of alkalis contain

A

OH- ions

45
Q

what are alkalis

A

soluble hydroxide bases

46
Q

what do bases do

A

neutralise acids

47
Q

examples of bases

A

metal oxides and hydroxides

48
Q

what does the pH scale do

A

it measures the potential for H+ ions in a solution
OR
it measures how acidic or alkaline a substance is

49
Q

what pH do neutral substances have

A

a pH of 7

50
Q

what pH do acids have

A

a pH lower than 7

51
Q

what pH do alkalis have

A

a pH higher than 7

52
Q

how can the pH of a substance be measured?

A

using a pH probe or universal indicator

53
Q

what happens in neutralisation reactions between an acid and an alkali

A

hydrogen ions react with hydroxide ions to produce water

54
Q

What are strong acids

A

acids which completely ionise in an aqueous solution ( H+ ions are produced)

55
Q

what are weak acids

A

acids which only partially ionise an an aqueous solution

56
Q

examples of strong acids

A

Hydrochloric acid, nitric acid and sulfuric acid

57
Q

examples of weak acids

A

ethanoic acid, citric acid and carbonic acid

58
Q

what will a concentrated acid have more of

A

concentrated acids will have more moles of acid per unit volume than a weak acid

59
Q

how can a concentrated acid be made dilute

A

by adding water

60
Q

What happens to the concentration when the pH decreases by one unit

A

as pH decreases by one unit, the concentration increasers by a factor of ten
Eg: pH1 = 10 x 10 to the -1
pH2 = 10 x 10 to the -2

61
Q

1 dm3 in cm3

A

1000cm3

62
Q

how to go from mol/dm3 to g/dm3

A

multiply by Mr

63
Q

what is titration used for

A

to work out the concentration of an unknown solution to determine the volume of an acid or alkali needed for neutralisation

64
Q

word equation for neutralisation reaction between sodium hydroxide solution and dilute sulfuric acid

A

Sodium hydroxide + sulfuric acid -> sodium sulfate + water

65
Q

what name is given to the curve on surface of a liquid

A

meniscus - the water sticks to the side of the tube

66
Q

how does lithium react with water

A

bubbles slowly, floats, moves slowly

67
Q

how does sodium react with water

A

fizzes rapidly, floats, moves around

68
Q

how does potassium react with water

A

bubbles very quickly, flots, moves very quickly, flame produced

69
Q

how does rubidium react with water

A

sinks, melts into a ball, explodes with a flame

70
Q

what is produced when a group one metal reacts with water

A

hydrogen

71
Q

what is titration used for

A

to work out the volume of an acid or alkali needed for neutralisation, by working out the concentration of an unknown solution

72
Q

basic method of titration

A
  • put acid in burette
  • 25cm cubed of alkali in conical flask, measured with a bulb pipette
  • add a few drops of indicator
  • slowly add acid to the conical flask and swirl to mix it
  • stop adding acid when the colour changes or the end point is reached
    -note final burette reading and calculate the volume of acid used
  • repeat until 2 readings are within 0.1cm cubed of eachother
73
Q

what are concordant results

A

results within 0.10cm cubed of eachother

74
Q

neutralisation reaction between Sodium hydroxide and sulfuric acid

A
  • use a bulb pipette to add 25cm3 of sodium hydroxide to a conical flask
  • add 2-3 drops of methyl orange to the conical flask
  • add the sulfuric acid into the burette
  • slowly add the acid into the conical flask and swirl to mix
  • stop adding the acid when the solution in the conical flask turns yellow or has reached its end point
  • note the final volume reading of the sulfuric acid added to neutralise the alkali
75
Q

what are the two methods of extracting copper

A

Phyto mining and bioleaching

76
Q

what is Phyto mining

A

using plants to absorb metal from the soil and then they are harvested. they are then burned to produce ash which contains the metal compounds

77
Q

what is bioleaching

A

using bacteria to produce leachate solutions which contain the metal compounds

78
Q

what are metal compounds reacted with to produce solutions of copper compounds

A

acid
the solutions are then reacted with scrap iron (displacement reaction) to produce copper

79
Q

advantages of the metal extraction methods

A

-less energy required than traditional methods
- can be extracted from low grade ores
- no mining is required
- avoids moving, digging and disposing of large amounts of rock

80
Q

disadvantages of the metal extraction methods

A
  • reactions are slow to carry out
  • land is not available
  • only small amounts of metal is produced
81
Q

what is electrolysis

A

passing an electric current through ionic substances that are molten or in solution to break them down into elements

82
Q

what ions move to the cathode

A

positive ions

83
Q

what ions move to the anode

A

negative ions

84
Q

what happens at the cathode

A

reduction - positive ions gain electrons to become metal ions.

85
Q

what happens at the anode

A

oxidation - negative ions lose electrons

86
Q

what is mixed with aluminium

A

cryolite

87
Q

what does cryolite do

A

lowers the melting point of the metal to reduce energy costs

88
Q

what elements are the electrodes made from

A

carbon

89
Q

what happens with carbon and oxygen at the anode

A

carbon reacts with oxygen to produce CO2, so it needs to be continually replaced

90
Q

half equation for copper

A

Cu2+ + 2e- -> Cu

91
Q

half equation for sodium

A

Na- + e- -> Na

92
Q

half equation for Chlorine

A

2Cl- -> Cl2 + 2e-

93
Q

half equation for oxygen

A

2O2- -> O2 + 4e-

Chemistry (9 decks)

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