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C5 Chemical Changes Flashcards

(92 cards)

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1
Q

A salt

A

Compound formed during a neutralisation reaction when some or all hydrogen ions in an acid are replaced with metal ions or ammonium ions

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2
Q

Neutralisation reaction

A

When an acid and a base are added together they cancel each other out and form a neutral solution

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3
Q

How to make a salt by reacting a metal with an acid

A

Salt is formed by replacing hydrogen ions in the acid with metal ions or aluminum ions

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4
Q

The reaction between a metal and an acid

A

Metal + acid ——> salt + hydrogen

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5
Q

A salt formed between a metal and sulfuric acid or hydrochloric acid

A

Salt will be chloride if acid is hydrochloric acid

Salt will be sulphate if acid is sulphuric acid

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6
Q

Which species is oxidised and which is reduced
in a reaction

A

The species that loses electrons is oxidized

The species that gains electrons is reduced

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7
Q

The reaction between a metal oxide or metal hydroxide and an acid

A

Acid + metal oxide = corresponding salt + water

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8
Q

Why the reaction between a base and a dilute acid is a neutralisation reaction

A

If a base is added to an acidic solution the solution becomes less acidic and moves toward the middle of the pH scale

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9
Q

How alkalis are a subgroup of bases

A

An alkali is a water-soluble base

Bases which can be dissolved in water to furnish OH-ions

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10
Q

How to make a salt reacting a metal carbonate with a dilute acid

A

Dilute hydrochloric acid

Add powdered zinc carbonate to acid

Continue to add powder until excess amount

Filter mixture in beaker to remove excess zinc

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11
Q

What happens when ammonia react with acid

A

Formation of a salt of weak bases and strong acid

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12
Q

Balanced equation for neutralisation reaction

A

NaOH + HCl ————> NaCl + H2O

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13
Q

How to use universal indicator to classify as acidic or alkaline

A

Few drops of universal indicator solution is added to each substance at a time

The colour obtained is compared to pH chart to give pH of solution

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14
Q

pH scale

A

Measures how acidic or alkaline an object is

Lowest 0 highest 14

Pure water has pH 7

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15
Q

Alkali effect on solution

A

A base or an alkali takes up hydrogen ions

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16
Q

Example of alkali

A

Sodium hydroxide

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17
Q

Example of a neutral

A

Pure water

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18
Q

Example of a base

A

Copper oxide

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19
Q

Acidic chemical example

A

Hydrochloric acid

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20
Q

Relationship between alkalis and bases

A

Alkali is a base

A base that dissolves in water

Not all bases are alkali but all alkali is base

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21
Q

How the pH of a solution changes as acid or alkali is added

A

pH below 7 is acidic

pH above 7 is alkaline

Acid added = pH decreases

Alkali added = pH increases

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22
Q

Examples of strong acids

A

Hydrochloric acid (HCl)

Sulfuric acid (H2SO4)

Nitric acid (HNO3)

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23
Q

Examples of weak acids

A

Acetic acid

Citric acid

Carbonic acid

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24
Q

How an acid or alkali can be concentrated or dilute

A

By adding water to a concentrated acid or base, the solution is diluted

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25
How an acid or alkali can be strong
A strong acid is one that's nearly or completely ionised in water
26
How an acid or alkali can be weak
If it's only partially ionised in water
27
How concentration of hydrogen ions relates to pH number
As concentration of hydrogen ions increase the pH decreases
28
Acid
A substance that produces hydrogen ions when dissolved in water
29
The lower the pH solution...
...the more acidic it is
30
The higher the pH solution...
...the more alkaline it is
31
Indicator
A dye that changes colour depending on whether it's above or below a certain pH
32
Wide range indicator
Indicators which contain a mixture of dyes so gradually change colour over a broad range of pH
33
What are wide range indicators used for
Estimating the pH of a solution
34
Why is a pH probe more accurate than an indicator
When the probe is placed in solution you're measuring the pH is given on a digital display as a numerical value
35
How does a pH probe work
Attached to a pH meter can be used to measure pH electronically
36
What substance do acids form in water
H+ ions
37
What substance do alkalis form in water
OH- ions
38
Base
Substance with pH greater than 7
39
Neutralisation
The reaction between acids and bases
40
Neutralisation reaction word equation
Acid + base --------> salt + water
41
Neutralisation reaction symbol equation
H+(aq) + OH-(aq) ------> H2O(I)
42
What happens when an acid neutralises a base
The products are neutral (they have a pH of 7)
43
Use of titrations
Allow you to find out exactly how much acid is needed to neutralise a quantity of alkali
44
Titration experiment Steps 1-3
Using a pipette and pipette filter add a set volume pf alkali to conical flask Use funnel to fill a burette with some acid of known concentration - make sure to do this below eye level Record initial volume of acid in burette
45
Titration experiment 4-6
Using burette add acid to alkali a bit at a time giving conical flask a regular swirl Go slowly when you think the end-point is about to be reached Indicator changes colour when all alkali is neutralised Record final volume of acid in the burette and use it along with initial reading to calculate volume of acid used to neutralise alkali
46
In titration experiment why do you need to use funnel to fill burette with acid
You don't want to be looking up if some acid spills over
47
How to increase accuracy of titration
You need several consistent readings Repeat whole thing few times
48
Universal indicator
Used to measure pH of a solution because it can turn a variety of colours Each colour indicates a narrow range of pH values
49
What is universal indicator made of
Mixture of different indicators changes from red to violet
50
During titration when will you see colour change
At the end-point
51
What colour is litmus indicator
Blue in alkali and red in acids
52
What colour is phenolphthalein indicator
Pink in alkalis and colourless in acids
53
What colour is methyl orange indicator
Yellow in alkalis and red in acids
54
Reactvitiy series
List of metals in order of their reactivity towards other substances
55
The reactvity series order Top half
Potassium Sodium Lithium Calcium Magnesium
56
The reactvity series order Bottom half
Carbon Zinc Iron Hydrogen Copper
57
How are metals reactivity determined by
How easily they lose electrons
58
How to tell the speed of a reaction
Rate of which bubbles of hydrogen are given off
59
How to investigate reactivity of metals
By measuring temperature change of the reaction with acid or water over a time period
60
Metal reacts with water word equation
Metal + water ------> metal hydroxide + hydrogen
61
Calcium hydroxide
Ca(OH)2
62
Calcium reacts with water symbol equation
Ca + 2H2O ---------> Ca(OH)2 + H2
63
Name the metals which react with water
Potassium, sodium, lithium and calcium
64
Name the metals which don't react with water
Zinc, iron, copper
65
Oxidation
Gain of oxygen
66
Reduction
Loss of oxygen
67
2Mg + O2 --------> 2MgO Which is oxidised
Magnsium is oxidised to make magnesium oxide
68
2CuO + C ------> 2Cu + CO2 Which is reduced
Copper oxide is reduced to copper
69
What do metals need to be extracted from their ores chemically by reduction
Carbon
70
How are the metals higher than carbon extracted by
Electrolysis (expensive)
71
How are the metals lower than carbon extracted by
Reduction using carbon
72
Why are metals above and below carbon extracted differently
Carbon can only take oxygen away from metals which are less reactive than carbon
73
How to extract very unreactive metals
They are in Earth's form as the metal itself
74
Is the ionisation of a weak acid reversible reaction or irreversible
Reversible reaction
75
Equation of strong acid
HCl ----------> H+ + Cl-
76
Equation of weak acid
CH3COOH ------\ H+ + CH3COO- \------
77
How to increase rate of reaction of acid
If concentration of H+ ions is higher
78
pH of an acid or alkali
A measure of concentration of H+ ions in solution
79
What happens to concentration for every decrease of 1 on the pH
Concentration increases by a factor of 10
80
What us the general rule for pH
-x Factor H+ ion concentration changes by = 10
81
Which pH is stronger when they have same concentration weak or strong acid
Weak acid has more pH than strong acid if same concentration
82
What does concentration measure
How much acid there is in a certain volume of water
83
Metal reacts with oxygen equation
Metal + oxygen → metal oxide
84
Displacement reaction
When a more reactive element displaces a less reactive element from a compound
85
Why a displacement reaction may occur
More reactive metal has stronger tendency to lose electrons and form positive ions than less reactive metal
86
Example of displacement reactions using an ionic equation
Zn + CuSP4 ------> ZnSO4
87
How to use reactivity series to determine whether a reaction between a metal and different metal salt would happen or not
A metal will displace another metal from its salt solution if more reactive than the metal in the salt
88
How is carbon used to extract from an ore
Heating the metal oxide in the presence of the carbon
89
How is hydrogen used to extract from an ore
By reacting hydrogen directly with iron ore, iron and water are produced in place of iron and CO2
90
How are metals extracted
Electrolysis
91
Ionic equation for reaction between an acid and alkali
H+ + OH- ----------> H2O
92
Why are gold and silver found naturally as elements in Earth's crust
Unreactive

Chemistry (10 decks)

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