If you are looking make it a little bit easier for you in your IGCSE Chemistry exams, then you are definitely at the right website. In IGCSE chemistry exams there are many questions which are repeated.
This blog includes many of those repeat questions. By keeping these questions in mind, you can easily get quite a lot of marks in your bag. keeping your mind fresh for the tougher questions. I have also included the answers. I have collected these questions by analyzing over 10 years worth of question papers.
Note: These Questions-answers are not in any specific order!
But if your IGCSE Chemistry concepts are very weak, it will be difficult for you to make full use of these common question answers. Hence it might be better if you revise all the IGCSE Chemistry concepts within a short time, like a week or two using a revision guide.
You can get the extended version of this note “Edexcel IGCSE Chemistry Common Questions with Answers: Study for 75 minutes and get an A* in IGCSE Chemistry” on Amazon available in Kindle or paperback formats.
Sample Question: Explain, in terms of its structure and bonding, why magnesium oxide has a very high melting point. (4 marks)
Ans: Magnesium Oxide is giant ionic structure, it contains Mg2+ and O2- ions, there is high attraction between the oppositely charged ions, takes lots of energy to overcome.
Ans: Diamond/Graphite/SiO2 is giant covalent structure, there are strong covalent bonds throughout the whole structure, which takes lots of energy to break.
Ans: i) The rate of forward and backward reaction are equal
ii) The concentration of reactant and products are constant.
Ans: Energy is released when bonds are made, energy is absorbed when bonds are broken, in an exothermic reaction more energy is released during bond making than absorbed while bond breaking.
(Practice: Explain in terms of bonding why heat is absorbed in endothermic reaction?)
Ans: Cracking produces smaller hydrocarbons, smaller hydrocarbons have greater demand, they are easier to burn, and also cracking produces more reactive alkenes.
Ans: They react because SiO2 is acidic while CaO is basic. This is a neutralization reaction.
Ans: Magnesium loses 2 electrons to form a Mg2+ ion, 2 chlorine atoms gains one electron each to form two Cl– ions. There is attraction between the oppositely charged ions.
Practice: Na reacting with Cl, Na reacting with O.
Ans: Because they have the same number of electrons in the outer shell.
Ans: It is the average mass of all the isotopes of an element. The mass of each isotope is in the scale of Carbon-12.
Ans: Take a clean nichrome wire, take solid M on the tip of the wire, then using the wire put the solid M in the blue part of the Bunsen burner flame.
Ans: In solid state the ions are not free to move and conduct electricity.
Ans:
Choose any two from three:
Ans: It means compounds having same molecular formula but different structural formula.
Ans: Hydrated Iron (III) Oxide
Ans: Air/Oxygen and Water.
Ans: Choose any two
Galvanizing, Painting, alloying, coating with tin.
Ans: The reaction is reversible.
Ans: Add few drops of the liquid to anhydrous copper(II)sulfate, if the liquid is water/contains water, it will turn from white to blue.
Ans: Take sample of the water and heat it, if it boils at 100°C then water is pure.
Ans: Compounds made of hydrogen and carbon only.
Sample Question 1: Explain how the covalent bonds in the water molecule hold the hydrogen and oxygen atom together? (2 marks)
Ans: The positive nuclei of both the oxygen and hydrogen atom are attracted towards the shared electron pair.
Sample Question 2: Explain how hydrogen and bromine atoms are held together in a molecule of hydrogen bromide? (2 marks)
Ans: The positive nuclei of both the hydrogen and bromine atom is attracted towards the shared electron pair.
Sample Question: Explain why water has a much lower melting point than sodium oxide. (2marks)
Ans: There are weak intermolecular attraction between the water molecules, which takes low energy to overcome. There is high attraction between the Na+ and O2- ions, which take lots of energy to overcome.
Sample Question: State a raw material used as the source of each gas. (2 marks)
Nitrogen: Air
Hydrogen: Natural Gas
Ans: Iron
Sample Question: Why is iron malleable? (2 marks)
Ans: Iron is malleable because when force is applied the particle/cations/ions (do not write molecules!!) are able to slide over each other.
Sample Question: Why is iron a good conductor of electricity? (2 marks)
Ans: Iron structure has delocalized electrons, which are able to move around and conduct electricity.
Ans:
Fluorine: Yellow
Chlorine: Green
Bromine: Reddish brown
Iodine: black
Ans:
Fluorine: gas
Chlorine: gas
Bromine: liquid
Iodine: solid
Ans: Contains carbon to carbon double bond.
Ans:
Iron ore/Haematite/Fe2O3
Coke/carbon/C
Limestone/CaCO3
Ans:
Aluminium: Bauxite (Al2O3)
Ans: A catalyst is a chemical which increases the rate of reaction without getting used up itself.
Ans:
Similarities:
Differences:
Ans: A reaction in which heat is released.
Ans: A catalyst provides an alternative route for the reaction to occur which has less activation energy.
Ans: At higher temperature, particles move faster collision frequency increases. More number of particles have higher energy than the activation energy, hence more number of useful collisions occurs.
Ans: Methane (CH4)
Ans: It is a process in which large hydrocarbons are broken down to smaller hydrocarbons with the help of catalyst or heat.
Ans: Unsaturated hydrocarbons turns bromine water from orange to colorless.
Ans:
Ans: By using a fractionating column, the crude oil is heated and passed into tower. Fractions condense at different levels of the towers, as different fractions have different boiling points.
Ans: Alkane: CnH2n+2
Alkene: CnH2n
Ans: Breaks down/decomposes/decays by bacteria/microbes/microrganisms.
Sample Question: Describe how she could use solutions of lead (II)nitrate and sodium bromide to obtain a pure, dry sample of lead(II)Bromide. (5 marks)
Ans: Mix the solutions of lead (II) nitrate and sodium bromide in a beaker, solid lead (II) bromide is formed. Filter to remove solid lead (II) bromide. Wash it with distilled water. Then leave it to dry.
Ans: Isotopes are atoms of the same element with the same proton number but different neutron number.
Ans: i) Magnesium burns with a bright white flame.
ii) A white solid is formed
Eg. MgO – basic oxide
Na2O- basic oxide
SO2 – acidic oxide
CO2– acidic oxide
Sample Questions:
State the condition that causes incomplete combustion. (1 mark)
Ans: lack of supply of air/oxygen.
Identify the poisonous gas produced. (1 mark)
Ans: Carbon monoxide
Explain why this gas is poisonous. (2 marks)
Ans: It attaches more efficiently with hemoglobin than oxygen, hence hinders the transportation of oxygen.
Ans: It causes acid rain, acid rain causes plants to die/damages monuments made of limestone/ kills fish/ increases soil pH.
Sample question: What property of these polymers prevents them from biodegrading? ( 1 mark)
Ans: They are inert/unreactive.
Ans: Methyl orange/phenolphthalein indicators gives a sharp color change whereas universal indicator does not.
Sample question : Indium is a metal in group 3 of the periodic table .
Describe the structure and bonding in indium (3 marks)
Ans: Indium structure has cations and delocalized electrons, there is high attractions between the cations and delocalized electrons.
Remember: Catalyst increases the rate of reaction, without getting used up itself, so their mass will be unchanged.
Sample question: In the first experiment the student added 1 g of solid A.
Describe what he could do with the contents of the conical flask at the end of the experiment to show that A was a catalyst, and not a reactant. (2 marks)
Ans: Separate solid A and weigh, if the mass is the same as before then it’s a catalyst.
Made up question:
A(g) + B(g) → C(g) + D(g)
What happens to the rate of reaction when pressure is increased? ( 1 mark)
Ans: Rate of reaction increases.
Explain your prediction in terms of the particle collision theory. (2 marks)
Ans: At higher pressure particles are closer together, collision frequency increases, hence rate of reaction increases.
Sample question: Explain, in terms of its structure, why graphite can act as lubricant (2 marks)
Ans: In graphite when force is applied, the layers can slide over each other.
Sample question: The structure of graphite has one feature in common with that of the metals. This feature allows graphite to conduct electricity.
Suggest what is this feature is and why it allows graphite to conduct electricity.
Ans: Graphite structure has delocalized electrons, which can move around to conduct electricity.
Ans: precipitation reaction
Sample question: State two observations you would make when dilute nitric acid is added to solid lead (II) carbonate
Ans:
Sample question: Describe a chemical test to show that the gas evolved at the positive electrode is chlorine. (2 marks)
Ans: Chlorine gas bleaches a damp litmus paper.
Ans: carbon/platinum
Ans: carbon dioxide turns limewater milky.
Ans: Fermentation
Ans: it acts as the catalyst.
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