This page contains the AQA GCSE Chemistry C5 Chemical Changes Questions and kerboodle answers for revision and understanding Chemical Changes.This page also contains the link to the notes and video for the revision of this topic.
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C 5.1 The Reactivity Series AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers : Page No. 85
- a. Answer. Reaction of lithium with water
Lithium + water → lithium hydroxide + hydrogen
2Li (s) + H2O (aq) = 2LiOH (aq) + H2 (g)
- Answer. Reaction of zinc with hydrochloric acid
Zinc + Hydrochloric acid → Zinc chloride + Hydrogen
Zn (s) + 2HCl (aq) → ZnCl2 (s) + H2 (g)
- Answer.
When the magnesium ribbon reacts with dilute sulphuric acid, we can see the following observation
Bubbles of hydrogen gas will be released. Magnesium ribbon will dissolve to form magnesium sulfate. The test tube will also become warm as the reaction is exothermic.
- Answer.
Metal + Acid = Salt + Hydrogen
- Answer.
Mg (s) + H2SO4 (aq) = MgSO4 (aq) + H2 (g)
Magnesium + Sulphuric Acid = Magnesium sulphate + hydrogen.
- Answer.
These metals placed are found at the bottom of the reactivity series. Hence, they are very unreactive. Gold and platinum are even known as noble metals. They are not affected by air, water and even by chemicals. Since they have bright lustre and resistant to reaction with air, water and chemicals which makes them useful to make jewellery.
- Answer.
Potassium, lithium, sodium are stored in oil as they all react with water producing lots of heat. As a result, hydrogen evolved catches fire. They cannot be kept in air also because air contains moisture or water vapour. These are kept under kerosene to avoid contact with both air and water.
- Answer.
Zinc is more reactive than tin. Which may react with food items and make it unfit for health. Therefore, food cans are plated with tin but no zinc.
- Answer.
Aluminium reacts with air and forms protective covering of aluminium oxide on its surface that further protects the surface of the aluminum and prevents it from corrossion. Therefore they are ideal to be used outdoors.
- Answer.
4Fe + 3O2 = 2Fe2O3
There is 1:2 ratio between iron oxide and iron. One mole of iron oxide gives 2 moles of iron. 112 g of iron when completely oxidises forms 160 g of iron oxide. Hence, 2.8 of iron will form (160/112)*2.80 = 4g of iron oxide
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C5.2 Displacement Reactions AQA GCSE Chemistry C5 chemical Changes Kerboodle Answers : Page No. 87
- a. Answer.
In the reaction between iron and zinc sulphate
The reaction will not take place as iron is less reactive than zinc so it will not displace zinc from zinc sulfate.
- Answer.
Reaction between zinc and copper sulphate will take place as Zinc is more reactive than copper so it will displace copper from its solution. Zinc displaces copper from copper sulfate& forms zinc sulfate solution. This is indicated by color change from blue to colorless. CuSO4solutionhas a blue color while ZnSO4solutionis colorless. Zn(s) + CuSO4(aq) ->Cu(s) + ZnSO4 (aq).
- Answer.
Reaction between magnesium and iron(III) chloride will take place as magnesium being more reactive than iron displaces iron from iron chloride and forms magnesium chloride. Magnesium reacts with iron(III) chloride to form magnesium chloride displacing iron.
3Mg(s) + 2FeCl3(s) => 3MgCl2(s) +2Fe(s)
- Answer.
Carbon is higher in the reactivity series than zinc but is lower in the reactive series than magnesium. Carbon being more reactive than zinc can displace zinc from its oxide and form zinc and carbon dioxide. However, carbon cannot reduce magnesium from its oxide as it is less reactive than magnesium so it cannot displace magnesium. Therefore, magnesium can only be extracted by electrolysis.
- a. Answer.
Tungsten is less reactive than hydrogen and hence is displaced by hydrogen in tungsten oxide to form tungsten and water.
- a. Answer.
Zn (s) + Fe2+(aq) → Zn2+(aq) + Fe (s)
- Answer.
Zn = Zn2+ + 2e-
Fe2+ +2e- = Fe
Zinc is losing two electrons and hence zinc is getting oxidised. Iron (III) is gaining two electrons hence iron is getting reduced to iron.
- Answer.
Moles of Zinc = 3.25/65 = 0.05 moles ( Moles = Mass/Mr)
moles of iron sulphate = 50*0.50/1000 (Moles= C X V) = 0.025 moles
Zn (s) + FeSO4 (aq) → ZnSO4 (aq) + Fe (s)
Since the ratio required is 1:1 according to balanced chemical reaction, 0.025 moles of iron sulfate will react with 0.025 moles of zinc. Hence, zinc is in excess and iron sulfate is a limiting reagent.
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C5.3 Extracting Metals AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers: Page No. 89
- Answer.
Ores are naturally occurring rocks that contain metal or metal compounds in sufficient amounts to make it worthwhile extracting them. The method used to extract a given metal from its ore depends upon the reactivity of the metal.
- Answer.
Gold is a very inert metal, it doesn’t readily react with other things, so it is not found chemically combined with other materials. Silver is less inert than gold, sometimes it is found in the metallic state, but often as compounds of silver such as, silver chloride, etc.
- Answer.
Since platinum is found in the native state, it means platinum is unreactive and is placed lower in the reactivity series. As it is noble metal and unreactive it will maintain its metallic luster and is best suited for making jewelry.
- a. Answer.
Zinc oxide + Carbon = Zinc + Carbon Monoxide
Zinc is getting reduced and carbon is getting oxidised.
- Answer.
ZnO (s) + C (s) = Zn (s) + CO (g).
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C5.4 Salts From Metals AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers : Page No. 91
- Answer. Metal and acid react to form a salt and hydrogen. The metal has to be more reactive than hydrogen.
metal + acid → salt + hydrogen
- a. Answer.
Copper sulphate cannot be prepared by adding copper to sulphuric acid because copper is not an active metal; its activity is less than that of hydrogen in the activity series so it cannot displace hydrogen from the acid and form a salt.
- Answer.
Potassium is never prepared by reacting potassium with hydrochloric acid because the reaction between potassium and hydrochloric acid is very violent, even explosive. On contact with the acid the reaction rapidly releases heat and hydrogen.
- a. Answer. Iron when reacted with sulphuric acid forms iron sulphate and hydrogen gas.
Fe (s) + H2SO4 (aq) = FeSO4 (aq) + H2 (g).
- Answer- Zinc when reacted with hydrochloric acid forms zinc chloride and hydrogen gas.
Zn (s) + 2HCl (aq) = ZnCl2 (aq) + H2.
- a. Answer Ionic equation of the reaction with zinc and dilute hydrochloric acid
– Zn (s) + 2 H+(aq) → Zn2+(aq) + H2(g).
- Answer- Oxidation half equation in which zinc loses two electrons
: Zn = Zn2+ + 2e-
Reduction half equation in which hydrogen ion gains two electrons.
: 2H+ + 2e- = H2.
- Answer.
Reaction between Zinc and hydrochloric acid is a redox reaction as In this reaction, zinc is getting oxidised as it is losing electrons and hydrogen is getting reduced as it is gaining electrons. Since both oxidation and reduction taking place in the same reaction, it is a redox reaction.
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C5.5 Salts From Insoluble Bases AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers : Page No. 93
- Answer. Acid base reaction is a neutralization reaction in which acid and base reacts to form salt and water.
Acid + alkali → salt + water.
- Answer.
Zinc oxide and hydrochloric acid reacts to form zinc chloride and water
Zinc oxide + hydrochloric acid ===> zinc chloride + water
ZnO + HCl —> ZnCl2 + H2O
- a. Answer.
Sodium Bromide = NaBr
- Answer.
Magnesium Fluoride = MgF2
- Answer.
Potassium nitrate = KNO3
- Answer.
Aluminium Sulphate = Al2(SO4)3
- Answer.
Take a clean beaker (250 ml) and put the powdered impure sample of copper sulphate in it. Add distilled water and stir the contents gently with the help of a glass rod. In order to make the solution more clear add two or three drops of concentrated sulphuric acid in it. Heat the solution in the beaker to 60-700C on a wire gauze. Stir it continuously and add more impure copper sulphate until no more of it dissolves. Filter the solution and collect the filtrate in a china dish. Place the china dish over wire gauze kept over a tripod stand and heat it gently (do not boil).
As the solution gets heated, stir it with a glass rod.
This helps in uniform evaporation and prevents the formation of a solid crust. When the volume of the solution reduces to one-half, take out a drop of the concentrated solution on one end of the glass rod and cool it by blowing air. Formation of thin crust indicates that it reaches to the crystallization point. Turn off the burner, cover the dish with a watch glass, and keep it undisturbed. As the solution cools down, crystals separate out. Slow cooling ensures better crystallization. Decant the mother liquor and wash the crystals with a thin stream of cold water with the help of a wash bottle. Dry the crystals by pressing them gently between sheets of filter paper.
- a. Answer. Lithium oxide and sulphuric acid reacts to form lithium sulphate and water.
Li2O (s) + H2SO4 (aq) = Li2SO4 (aq) + H2O (l) .
- Answer.
Moles of sulphuric Acid = 15*2/1000 ( moles = Concentration X Volume)= 0.03 moles
Since there is a 1:1 ratio of sulfuric acid and lithium salts, the moles of lithium salt formed will be 0.03 moles.
Mass of 0.03 moles of lithium salt = moles * Mr ( Mr of lithium sulfate = 110 g)
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C 5.6 Making More Salts AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers: Page No. 95
- a. Answer. Acid and alkali reacts to form salt and water in a neutralization reaction.
Acid + base → salt + water.
- Answer.
H+ and OH- reacts to form water.
H+ (aq) + OH- (aq) = H2O (l).
- Answer.
Acid and the metal carbonate react to form salt, water and carbon dioxide.
Acid + metal carbonate → salt + water + carbon dioxide.
- a. Answer.
Lithium chloride is produced by the treatment of lithium carbonate and hydrochloric acid.Lithium chloride is produced by the treatment of
lithium carbonate and hydrochloric acid. Lithium
carbonate is soluble. We will first titrate the
lithium carbonate with hydrochloric acid in the
presence of indicator to know the exact volume of
lithium carbonate and hydrochloric acid that will
react completely in a neutralisation reaction.
When the exact volume is known the same reaction
will be carried out but this time without the
indicator. After the reaction lithium chloride,
carbon dioxide and water will be formed. Carbon
dioxide will escape and the aqueous solution of
lithium chloride will be evaporated to evaporate
the water and lithium chloride crystals will be
collected.
- Answer.
Lithium carbonate reacts with hydrochloric acid to form lithium chloride, carbon dioxide and water
Li2CO3 + 2HCl —> 2LiCl + CO2 + H20.
- a. Answer.
Barium carbonate react with nitric acid to form barium nitrate, water and carbon dioxide.
BaCO3 (s) + 2HNO3 (aq.) –> Ba2+ (aq.) + 2(NO3-) (aq.) + CO2 (g) + H2O (l)
- Answer.
When acids and metal carbonates react, hydrogen ions and carbonate ions react to form water and carbon dioxide.
2H+(aq) + CO32-(aq) → H2O(l) + CO2(g)
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C5.7 Neutralisation and the pH Scale AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers : Page No. 97
- a. Answer.
All bases do not dissolve in water. Soluble bases are known as alkali. If a base does dissolve in water, we call it an alkali.
- Answer.
All alkalis are soluble and have a pH greater than 7.
- Answer.
Potassium hydroxide when dissolved in water dissociates into potassium ion and hydroxide ion.
KOH (s) = K+ (aq) + OH- (aq).
- a. Answer.
Acids produce hydrogen ions, H+ when dissolved in water or in aqueous solutions.
- Answer.
When hydrobromic acid dissolved in water then is dissociates into hydrogen ion and bromide ions.
HBr (aq) + H2O (l) = H3O+ (aq) + Br– (aq)
The pH of the solution will decrease as H+ ions will be formed in the solution.
- Answer.
We can distinguish distilled water, sodium hydroxide solutions and ethanoic acid solutions with the color they produce when the universal indicator is added. Water being neutral will give a green color. Sodium hydroxide being strongly alkaline will produce a purple color and ethanoic acid being a weak acid will produce a red-orange color.
- Answer.
When a strong acid is added slowly to strong alkali, the pH will decrease as the alkali will start to get neutralized with the acid. One the neutral pH is reached, all the strong alkali will have been used up. Adding the acid further will decrease the pH and will make the solution acidic as the acid will be in excess.
- Answer
PH paper is used to determine if a solution is
acidic, basic or neutral. This is
determined by dipping part of the paper into a
solution of interest and watching the
color change. The packages that pH paper comes in
often includes a color-coded
scale indicating the pH that something has when
the paper turns a certain color. For
instance, if the paper turns a dark
greenish-blue, the pH may likely be around 11 to
14.
PH meters measure a solution’s pH by measuring
the electrical potential difference
between the pH electrode and a reference
electrode. The meter then coverts this
potential to a pH reading. They offer readings to
0.01 pH unit, and are useful for
advanced science, college, or research work that
requires this level of precision.
Advantages
There are many benefits to using pH strips and
papers. Like indicator solutions, they
are quick and easy to use, and compared to pH
meters, they are much less
expensive. pH papers are portable, easy to store,
and well suited for field work. In
classrooms, pH strips can be pasted into a lab
notebook to retain experimental
Results.
Disadvantages
While pH strips and papers give more accuracy and
precision than liquid indicators,
they are still inferior to pH meters. Solution
color and turbidity are also concerns
when using pH strips and papers—colorless
solutions give the best results.
There are drawbacks to using pH indicators. The
test sample should be fairly
colorless to clearly see the indicator’s color
change. Also, the indicators inherently
measure pH at a low accuracy.
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C5.8 Strong and Weak Acids AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers: Page No. 99
- Answer.
The beaker with the ethanoic acid will have a higher pH and the beaker with nitric acid will have a lower pH.
- a. Answer.
=pH= -log [1.0 × 10-5 ]
pH= 5
- Answer.
Neutral Solution has a pH of 7 so the H+ Concentration will be 1.0X10^-7 mol/dm3.
- Answer.
Propanoic Acid is a weak acid is it partially dissociated to give H+ions when dissolved in water. On the other hand, nitric acid is completely dissociated to give H+ ions therefore is considered as a strong acid.
4.Answer.
The pH is a measure of the number of hydrogen ions in solution. The strength of an acid depends on the concentration of the solution and whether or not it fully ionizes or partially ionizes in water. A Strong acid will be completely dissociated to give the H+ ions and will be diluted which will neutralize the H+ to give the higher pH value. On the other hand, the weak acid being concentrated will not dissociate to give enough H+ ions that can give a high pH value.
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Summary Questions AQA GCSE Chemistry C5 Chemical Changes : Page No. 100
1.a. Answer.
X reacts with sulphuric acid and will form a sulphate salt with the evolution of hydrogen gas. X will be more reactive as it is higher in the reactivity series so it will react completely.
X + sulfuric acid → X sulfate + hydrogen
X(s) + H2SO4(aq) → XSO4(aq) + H2(g)
- Answer.
Magnesium reacts very slowly with water, calcium reacts vigorously with water.
We do not know how much less reactive than calcium and more reactive than magnesium the element X is and so cannot predict whether the reaction will be slow like magnesium or more vigorous.
- i. Answer.
X is more reactive than copper so it will displace copper from its salt.
The more reactive metal X displaces less reactive copper. X dissolves into solution and copper metal deposited as a brown solid. The blue colour of copper nitrate will disappear as copper will be displaced.
X(s) + Cu(NO3)2(aq) → X(NO3)2(aq) + Cu(s)
- Answer.
X(s) + Cu2+(aq) → X2+(aq) + Cu(s).
iii. Answer.
X(s) → X2+(aq) + 2e–
X atoms oxidised as lose 2 electrons.
Cu2+(aq) + 2e– → Cu(s) Cu2+ ions reduced as gain 2 electrons.
- i. Answer.
Y will be placed Just above copper in the reactivity series.
- Answer.
No change / no reaction as Y less reactive than magnesium so cannot displace it from solution of one of its compounds.
Answer 2 a)
- Answer.
Carbon and copper oxide will React as carbon is more reactive than copper and can displace copper.
- Iron + zinc nitrate [1 mark]
Answer.
- Iron with Zinc Nitrate cannot react is iron being less reactive than zinc cannot displace zinc.
iii. Iron with magnesium oxide will not react as iron being less reactive than magnesium cannot displace magnesium.
- Magnesium will react with copper sulphate as magnesium being more reactive than copper sulphate will displace copper from copper sulphate.
- Answer.
Carbon + copper(II) oxide → copper(II) oxide + carbon dioxide.
C(s) + 2CuO(s) → 2Cu(s) + CO2(g).
Magnesium + copper(II) sulfate → magnesium sulphate + copper.
Mg(s) + CuSO4(aq) → MgSO4(aq) + Cu(s).
- a. i. Answer.
Aluminium + iron(III) oxide → aluminium oxide + iron.
2Al + Fe2O3 → Al2O3 + 2Fe.
- Answer.
Displacement reaction as the more reactive metal displaces the less reactive metal from its salt.
- Answer.
Aluminium will react more vigorously with copper(II) oxide than with iron(III) oxide. The difference in reactivity between aluminium and copper is more than aluminium and iron therefore the reaction will be more rigorous.
- Answer.
Mixture of aluminium oxide and iron will not react as iron being less reactive will displace aluminium from aluminium oxide.
- Answer.
Aluminium is highly reactive so it should react with air, moisture if used in outdoor but still it is used in windows and outdoor. Aluminium reacts with air and form aluminum oxide which coats the surface of the metal and protects it further. Therefore it is used widely used in the outdoors.
- a. Answer.
During roasting, lead sulphide reacts with oxygen and form lead oxide and sulphur dioxide.
Lead sulfide + oxygen → lead oxide + sulfur dioxide.
- Answer.
2PbS(s) + 3O2(g) → 2PbO(s) + 2SO2(g).
- Answer.
Lead oxide reacts with carbon to form and lead and carbon dioxide.
2PbO + C → 2Pb + CO2
- a. i. Answer.
Nickel (ll) oxide is an insoluble base that can react with sulphuric acid to form nickel sulphate and water.
- Answer.
NiO(s) + H2SO4(aq) → NiSO4(aq) + H2O(l).
iii. Answer.
Neutralisation Reaction as it is a reaction between an acid and a base.
- Answer.
Nickel oxide and sulphuric acid are reacted. Nickel oxide should be added in excess and unreacted nickel oxide can be filtered off. After reaction, the solution will contain nickel sulphate and water. The solution can be evaporated to evaporate the water leaving nickel sulphate crystals behind which can be dried on the filter paper.
6.a. Answer.
Lithium hydroxide reacts with sulphuric acid to form lithium sulphate and water.
2LiOH(aq) + H2SO4(aq) → Li2SO4(aq) + 2H2O(l).
- Answer.
Iron oxide reacts with nitric acid to form iron nitrate and water.
Fe2O3(s) + 6HNO3(aq) → 2Fe(NO3)3(aq) + 3H2O(l).
- Answer.
Zinc metal reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g).
- a. i. Answer.
Concentration of 0.50 mol/dm3 means that 0.50 mol of solute is dissolved in 1dm3 of solution.
- Answer.
0.50 mol/dm3 nitric acid = 0.50 *63 (Mr of nitric acid) g/dm3
31.5g/dm3 nitric acid,
0.50 mol/dm3 of methanoic acid = 0.50*46 (Mr of methanoic acid) g/dm3
23.0g/dm3 methanoic acid.
- i. Answer.
Methanoic acid is a weak acid has higher pH than nitric acid which is a strong acid.
- Answer.
Nitric acid is a strong acid so all the HNO3 molecules ionise in water. Methanoic acid is a weak acid so most of its molecules stay un-ionised / only a few molecules ionise and split up to form H+(aq) ions in a reversible reaction so fewer H+(aq) ions in a given volume of methanoic acid solution compared with same volume of nitric acid solution.
C Answer.
Ethanoic acid, Propanoic Acid. All carboxylic acids are weak acids.
- i. Answer.
1.0 × 10−1mol/dm3
- Answer.
-log [1X10-3] mol/dm3
pH = 3.0.
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Practice Questions AQA GCSE Chemistry C5 Chemical Changes Kerboodle Answers: Page No. 101
01.1. Answer.
The one that produce highest fizzing is the most reactive and the one that has no fizzing is least reactive so the order is :
B (least reactive)D-C-E-A (most reactive)
01.2. Answer.
The test for hydrogen is a squeaky pop test. When a split is brought near to the mouth of hydrogen gas it burns with a squeaky pop.
lit splint (goes out with a squeaky) pop.
01.3. Answer.
The variable that needs to be controlled in the experiment are :- same amount of metal and the similar temperature of water in all the test tubes.
01.4. Answer. A(OH)2
A is group 2 so will have +2 charge and OH- has a charge of -1 so the formula will be A(OH)2
2.1 Copper is less reactive than hydrogen so cannot displace hydrogen from acid therefore copper metal does not react with dilute sulphuric acid.
02.2. Answer.
The student heated the sulphuric acid To increase the rate of reaction as increase in temperature increases the rate of reaction.
02.3. Answer.
The acidic colour can either be red, orange or yellow.
02.4. Answer.
To ensure all the acid is used up we should add copper oxide is excess.
03.1. Answer.
When iron reacts with copper sulphate solution, iron will displaced copper so brown colour of copper will be formed and blue coloured copper sulphate solution will change into pale green iron sulphate.
03.2. Answer.
When magnesium reacts with iron sulphate, magnesium displaced iron and forms magnesium sulphate. Pale green solution of iron sulphate will change to colourless solution of magnesium sulphate.
03.3. Answer.
copper does not react with magnesium sulfate as copper is less reactive than magnesium so copper cannot displace magnesium sulphate from its salt.
03.4. Answer.
Fe + Cu2+ → Fe2+ + Cu
03.5. Answer.
Fe2+ + 2e- → Fe
(Fe2+ ions are reduced because they have) gained electrons.
04.1. Answer.
To form magnesium nitrate, we need to react magnesium carbonate with nitric acid. Magnesium carbonate is added in excess and excess magnesium carbonate is filtered off. The reaction mixture will now be solution of magnesium nitrate with water which can be separated by crystallization. The solution is evaporated until all the water is evaporated and crystals of magnesium nitrate are formed.
04.2. Answer.
Since ethanoic acid is a weak acid than nitric acid it will react slowly so
Effervescence with ethanoic acid would be slower (than with nitric acid).
04.3. Answer.
correct equation scores 2 marks CH3COOH ⇌ CH3COO- + H+
04.4. Answer.
Since the difference in the pH is 3 so the concentration will 1,000 times greater.
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This page contains the detailed and easy notes for AQA GCSE Chemistry Periodic Table for revision and understanding Periodic Table.
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AQA GCSE Paper 1: Complete Revision Summary
CHEMICAL CHANGES
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4.4 CHEMICAL CHANGES
- Reactivity of Metals
- Reactivity Series
- Extraction of Metals
- Acids and Bases
- Neutralization
- Making Soluble Salts
- Making Insoluble Salts
- Titrations
- Electrolysis
- Electrolysis of molten compounds
- Electrolysis of aqueous solutions
- Electrolysis of Aluminium
REACTIVITY SERIES
Metal + Dilute Acids = Salt + Hydrogen
Metal + Water = Metal Hydroxide + Hydrogen
DISPLACEMENT REACTION
More reactive metal will displace the less reactive metal from its salt solution.
Magnesium(More reactive metal) + Zinc sulphate (Less reactive salt ) = Magnesium sulphate (More reactive metal displaces the less reactive) + Zinc
Lead + Magnesium Sulphate = No reaction
(Less reactive metal cannot displace the more reactive metal)
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METAL EXTRACTION
MINERALS
Minerals are the rocks which contains metal.
ROCKS
Rocks are the minerals from which metals can be extracted profitably.
REDUCTION OF METAL OXIDES
Since most of the metals exist in the form of oxides, they can be extracted by reducing the ore.
By HYDROGEN
All the metal below hydrogen can be reduced by hydrogen
BY CARBON
All metal below carbon can be extracted by carbon
BY ELECTROLYSIS
Metals that are above carbon and hydrogen will be extract by Electrolysis
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OXIDATION AND REDUCTION
Oxidation
- Gain of Oxygen
- Loss Of hydrogen
- Loss of electrons
C + O2 CO2
CH4 + O2 CO2 + H2O
2Cl– Cl2 + 2e
Reduction
- Loss of Oxygen
- Gain of Hydrogen
- Gain of electrons
CuO + Zn Cu + ZnO
H2S + Cl2 2HCl + S
Na+ + e– Na
Copper Oxide + Hydrogen Copper + Water
CuO + H2 Cu + H2O
Zinc Oxide + Carbon Zinc + Carbon Dioxide
2ZnO + C 2Zn + CO2
ACIDS BASES and ALKALI
The substance which have pH less than 7.
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Strong Acids
- They completely dissociated in water to release H+ ions
- Hydrochloric Acid HCl
- Sulphuric Acid H2SO4
- Nitric Acid HNO3
- Phosphoric Acid H3PO4
- HCl H+ + Cl–
- pH = 1-3
Weak Acids
- They are partially dissociated in water to release H+ ions
- Vinegar: Ethanoic Acid
- Lemon: Citric Acid
- CH3COOH CH3COO– + H+
- pH = 5-7
The substance which have pH greater than 7.
- Metal Oxides, Metal Hydroxides, Metal Carbonates
- Lithium Oxide, Lithium Carbonate, Lithium Hydroxide
- Alkali are the soluble bases. So bases that can dissolve in water.
- Alkali metal hydoxide
- They release hydroxide ions when dissolved in water.
INDICATORS
| Acids | Bases |
| Taste Sour | Taste Bitter |
| Not soapy | Feels soapy |
| have pungent small | do not have a pungent smell |
| When ionize give hydrogen ions | Give hydroxide ions |
| Turns blue litmus red | Turns red litmus Blue |
| eg Hydrochloric Acid | eg Sodium Hydroxide |
| Sulphuric Acid |
NEUTRALIZATION REACTION
Acid + Base Salt + Water
Metal Acid
Hydrochloric Acid -makes chloride salt
Sulphuric Acid – makes sulphate salt
Nitric Acid – makes nitrate salt
Eg
Sodium Chloride + Water Sodium Hydroxide + Hydrochloric Acid
NaOH + HCl NaCl + H2O
Potassium Oxide + Sulphuric Acid Potassium Sulphate + Water
K2O + H2SO4 K2SO4 + H2O
Magnesium Hydroxide + Nitric Acid Magnesium Nitrate + Water
Mg(OH)2 +2HNO3 Mg(NO3)2 +2H2O
Calcium Carbonate + Sulphuric Acid Calcium Sulphate + Carbonate + Water
CaCO3 + H2SO4 CaSO4 + H2O + CO2
REACTIONS OF ACIDS
- Metal + Acid = Salt + Hydrogen
- Metal Oxide + Acid = Salt + Water
- Metal Hydroxide + Acid = Salt + Water
- Metal Carbonate + Acid = Salt Water + CO2
2Na + 2HCl 2NaCl +H2
Making Insoluble salts
Mix two soluble acids and Bases
The salt will come out as a precipitate
The precipitate is then filtered and dried.
The filter paper will contain an insoluble salt.
To determine the exact volume of acid and base required to make the salt, titration is carried out.
Making Soluble Salts
Mix the insoluble base into the aqueous solution of the acids.
Dissolve the base into the acid until no base can be dissolved.
Filter the solution to remove excess undissolved base.
The run off is then crystallized to remove all the water.
After evaporation the crystals will collect at the size of the vessel.
The crystals can then be dried.
ELECTROLYSIS
- Electrolysis – The breaking of ionic compound by passing electricity.
- Electrolyte – The substance that undergoes Electrolysis
- Electrode – The two conducting rods dipped in an electrolyte
- Cathode – Where Cations (+ve charge ions) go. So it is negatively charge electrode
- Anions – Where anions (-ve charge ions) go. So it is positively charged.
ELECTROLYSIS OF MOLTEN IONIC COMPOUNDS
Ionic compounds conduct Electricity when in molten or in solution as the ions are free to move when they’ are in solvent or dissolved in water.
Molten Sodium Chloride
NaCl Na+(goes towards cathode) + Cl–(goes towards anode)
Cathode Reduction
Na+ + e– Na(s)
Anode Oxidation
2Cl– Cl2(g) + 2e–
O – Oxidation
I – Is
L – Loss
R – Reduction
I – Is
G – Gain
ELECTROLYSIS IN SOLUTIONS
In Solution the water also gets ionized and dissociate into H+ and OH- which also competes with the ionic compounds ions to discharge.
Sodium Chloride Solution
Ions
H+ + OH–
Na+ + Cl–
At Cathode
2H+ + 2e– H2(g)
Rule – At the cathode, the element with least reacitivity will get discharged and gains electrons.
For that we have to look at the reactivity series
At Anode
2Cl– Cl2 + 2e–
For Anode, the rule is – Halide> OH– > other negative ions
Remaining Solution
Na+ + OH–
Potassium Sulphate solution
Ions
K+ + SO42-
H+ + OH–
At Cathode
2H+ + 2e– H2
At Anode
4OH– O2 + 2H2O + 4e–
Remaining Solution
K2SO4
ELECTROLYSIS OF ALUMINIUM OXIDE
Bauxite an ore of aluminium is used which contains aluminium in the form of aluminium oxide.
Al2O3 Al3+ O2-
Bauxite is mixed with cryolite. Cryolite lowers the melting point of aluminium oxide making it melt at a lower temperature.
At Anode
2O2- O2 + 4e–
Oxygen evolved reacts with graphite electrode forming carbon dioxide. Therefore, they are used up and needs regular replacing
At Cathode
Al3+ + 3e– Al(s)
O2 + C CO2
Baneer 6
Disclaimer:
I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it.
References:
BBC Bitesize
Wikipedia
Wikimedia Commons
Image Source:
Wikipedia
Wikimedia
Commons
Flickr
Pixabay
Make sure you have watched the above videos and are familiar with the key definations before trying these questions. It is also good to time yourself while doing these questions so that you can work on the speed as well.