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Chemistry > November Test - chemical changes > Flashcards

November Test - chemical changes Flashcards

acids and bases topic electrolysis topic

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
what is oxidation in terns of electrons
Oxidation is the loss of electrons
26
what is reduction in terms of electrons
reduction is the gain of electrons
27
oxidation of Zinc
Zn -> Zn2+ + 2e-
28
reduction of zinc
Zn2+ + 2e- -> Zn
29
which elements wont react with acids
Copper, Silver, Gold
30
which metals react with acids by producing bubbles of H2 gas
potassium, sodium, calcium, magnesium, aluminium, carbon, zinc, copper, tin, lead
31
equation of reactions of acids with metals
acid + metal -> salt + hydrogen
32
word equation for magnesium reacting with sulfuric acid
Magnesium + Sulfuric acid -> Magnesium sulfate + hydrogen
33
what are reactions of acids with metals known as
redox reactions - reduction and oxidation reactions
34
Half equations for magnesium reacting with sulfuric acid
Mg -> Mg2+ + 2e- 2H+ + 2e- -> H2
35
neutralisation reaction word equation
base + acid -> salt + water
36
how can acids be neutralised?
by adding a base or a carbonate
37
products of reacting an acid with a carbonate
acid + metal carbonate -> salt + water + carbon dioxide
38
word equation for neutralisation of copper oxide with sulfuric acid
copper oxide + sulfuric acid -> copper sulfate + water
39
word equation for neutralisation of copper carbonate with Hydrochloric acid
Copper carbonate + Hydrochloric acid -> copper chloride + water + carbon dioxide
40
how can soluble salts be made
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
Method of making soluble salt with HCL and Copper oxide
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
why do we use filter paper to dry the crystals, rather than place them in an oven to heat it dry
to avoid removing water of crystallisation and white anhydrous copper sulphate crystals could form
43
what are acids
substances which produce H+ ions in aqueous solutions
44
what do aqueous solutions of alkalis contain
OH- ions
45
what are alkalis
soluble hydroxide bases
46
what do bases do
neutralise acids
47
examples of bases
metal oxides and hydroxides
48
what does the pH scale do
it measures the potential for H+ ions in a solution OR it measures how acidic or alkaline a substance is
49
what pH do neutral substances have
a pH of 7
50
what pH do acids have
a pH lower than 7
51
what pH do alkalis have
a pH higher than 7
52
how can the pH of a substance be measured?
using a pH probe or universal indicator
53
what happens in neutralisation reactions between an acid and an alkali
hydrogen ions react with hydroxide ions to produce water
54
What are strong acids
acids which completely ionise in an aqueous solution ( H+ ions are produced)
55
what are weak acids
acids which only partially ionise an an aqueous solution
56
examples of strong acids
Hydrochloric acid, nitric acid and sulfuric acid
57
examples of weak acids
ethanoic acid, citric acid and carbonic acid
58
what will a concentrated acid have more of
concentrated acids will have more moles of acid per unit volume than a weak acid
59
how can a concentrated acid be made dilute
by adding water
60
What happens to the concentration when the pH decreases by one unit
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
1 dm3 in cm3
1000cm3
62
how to go from mol/dm3 to g/dm3
multiply by Mr
63
what is titration used for
to work out the concentration of an unknown solution to determine the volume of an acid or alkali needed for neutralisation
64
word equation for neutralisation reaction between sodium hydroxide solution and dilute sulfuric acid
Sodium hydroxide + sulfuric acid -> sodium sulfate + water
65
what name is given to the curve on surface of a liquid
meniscus - the water sticks to the side of the tube
66
how does lithium react with water
bubbles slowly, floats, moves slowly
67
how does sodium react with water
fizzes rapidly, floats, moves around
68
how does potassium react with water
bubbles very quickly, flots, moves very quickly, flame produced
69
how does rubidium react with water
sinks, melts into a ball, explodes with a flame
70
what is produced when a group one metal reacts with water
hydrogen
71
what is titration used for
to work out the volume of an acid or alkali needed for neutralisation, by working out the concentration of an unknown solution
72
basic method of titration
- 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
what are concordant results
results within 0.10cm cubed of eachother
74
neutralisation reaction between Sodium hydroxide and sulfuric acid
- 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
what are the two methods of extracting copper
Phyto mining and bioleaching
76
what is Phyto mining
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
what is bioleaching
using bacteria to produce leachate solutions which contain the metal compounds
78
what are metal compounds reacted with to produce solutions of copper compounds
acid the solutions are then reacted with scrap iron (displacement reaction) to produce copper
79
advantages of the metal extraction methods
-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
disadvantages of the metal extraction methods
- reactions are slow to carry out - land is not available - only small amounts of metal is produced
81
what is electrolysis
passing an electric current through ionic substances that are molten or in solution to break them down into elements
82
what ions move to the cathode
positive ions
83
what ions move to the anode
negative ions
84
what happens at the cathode
reduction - positive ions gain electrons to become metal ions.
85
what happens at the anode
oxidation - negative ions lose electrons
86
what is mixed with aluminium
cryolite
87
what does cryolite do
lowers the melting point of the metal to reduce energy costs
88
what elements are the electrodes made from
carbon
89
what happens with carbon and oxygen at the anode
carbon reacts with oxygen to produce CO2, so it needs to be continually replaced
90
half equation for copper
Cu2+ + 2e- -> Cu
91
half equation for sodium
Na- + e- -> Na
92
half equation for Chlorine
2Cl- -> Cl2 + 2e-
93
half equation for oxygen
2O2- -> O2 + 4e-

Chemistry (9 decks)

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