IGCSE Chemistry Practice Test 17

Correct: (B)

Condensation is the change from the gas state to the liquid state when particles lose energy.

Correct: (D)

Gas particles move most freely and at the highest speeds, so they spread out fastest.

Correct: (A)

In a solid the particles are held in a regular arrangement and can only vibrate about fixed positions.

Correct: (C)

Nucleon number = protons + neutrons = 6 + 6 = 12.

Correct: (A)

Isotopes have the same proton number but different neutron numbers, so their chemistry is the same.

Correct: (C)

Magnesium has 12 electrons arranged as 2 in the first shell, 8 in the second and 2 in the third shell.

Correct: (D)

The metal loses electrons and the non-metal gains them, forming oppositely charged ions.

Correct: (B)

An oxygen molecule has a double bond, O=O, between the two atoms.

Correct: (C)

Diamond is a giant covalent structure, and a large amount of energy is needed to break its many strong bonds.

Correct: (A)

Metallic bonding is the attraction between positive metal ions and a sea of delocalised electrons.

Correct: (B)

The ion gained 2 electrons, so the atom has 16 electrons and 16 protons: sulfur, in Group VI.

Correct: (D)

Moles = mass / Mr = 8 / 16 = 0.50 mol.

Correct: (D)

Volume = moles × 24 = 0.25 × 24 = 6.0 dm^3.

Correct: (B)

250 cm^3 = 0.250 dm^3, so moles = 0.50 × 0.250 = 0.125 mol.

Correct: (C)

Moles: C = 40/12 = 3.33, H = 6.7/1 = 6.7, O = 53.3/16 = 3.33; ratio 1 : 2 : 1 gives CH2O.

Correct: (A)

Percentage yield = (18 / 24) × 100 = 75%.

Correct: (A)

10 g CaCO3 is 0.10 mol, which makes 0.10 mol CaO = 0.10 × 56 = 5.6 g.

Correct: (D)

The empirical unit has Mr = 14; 42 / 14 = 3, so the molecular formula is C3H6.

Correct: (B)

Lead ions, Pb^2+, move to the negative cathode and gain electrons to form lead metal.

Correct: (C)

Copper is below hydrogen in the reactivity series, so copper ions are discharged and copper coats the cathode.

Correct: (C)

In electrolysis the anode is connected to the positive terminal and attracts negative ions.

Correct: (B)

Aluminium is above carbon in the reactivity series, so carbon cannot remove oxygen from aluminium oxide.

Correct: (A)

In the solid the ions are locked in place, but when molten or dissolved they can move to the electrodes.

Correct: (D)

An exothermic reaction releases thermal energy, warming the surroundings.

Correct: (D)

Energy must be supplied to break bonds, and energy is released when new bonds form.

Correct: (A)

Bonds broken = 436 + 242 = 678; bonds made = 2 × 431 = 862; ΔH = 678 – 862 = -184 kJ/mol.

Correct: (C)

Hydrogen reacts with oxygen in the cell and the only product is water.

Correct: (B)

Calcium carbonate only decomposes when heat energy is continuously supplied, so the process takes in energy.

Correct: (B)

At a higher temperature particles move faster, so a greater proportion of collisions have enough energy to react.

Correct: (C)

A catalyst offers a different reaction route needing less energy, and it is not used up.

Correct: (D)

Powder exposes more surface, so acid particles collide with the solid more frequently.

Correct: (A)

Hydrated copper(II) sulfate loses water on heating and regains it when water is added, so the change can go both ways.

Correct: (A)

There are 4 moles of gas on the left and 2 on the right, so higher pressure shifts the equilibrium towards ammonia.

Correct: (B)

Oxidation is the loss of electrons (OIL: Oxidation Is Loss).

Correct: (D)

A reducing agent donates electrons to another substance and is oxidised in the process.

Correct: (C)

Acid + carbonate → salt + water + carbon dioxide.

Correct: (C)

Strong alkalis have high pH values, around 13-14.

Correct: (D)

Insoluble salts are made by precipitation: mixing the two solutions forms solid barium sulfate, which is filtered, washed and dried.

Correct: (A)

Both reactants are solutions, so titration with an indicator is used to find the exact volumes that react.

Correct: (B)

Aluminium oxide reacts with both acids and alkalis, so it is amphoteric.

Correct: (D)

Barium ions form insoluble white barium sulfate with sulfate ions.

Correct: (C)

In every acid-alkali neutralisation, hydrogen ions react with hydroxide ions to form water.

Correct: (B)

Group I metals become more reactive down the group; potassium reacts more violently with water than lithium.

Correct: (A)

Chlorine is more reactive than bromine, so it displaces bromine, giving an orange solution.

Correct: (B)

Transition elements form coloured compounds and many act as catalysts, unlike Group I metals.

Correct: (A)

A complete outer electron shell is very stable, so noble gas atoms do not gain, lose or share electrons.

Correct: (C)

Magnesium is the highest of these metals in the reactivity series, so it reacts most vigorously.

Correct: (D)

Carbon monoxide reduces iron(III) oxide: Fe2O3 + 3CO → 2Fe + 3CO2.

Correct: (A)

Stainless steel contains chromium (and often nickel), which prevents rusting.

Correct: (C)

Rusting is the corrosion of iron and needs both water and oxygen (air).

Correct: (B)

Chlorine sterilises the water by killing microbes that cause disease.

Correct: (D)

Air is approximately 78% nitrogen and 21% oxygen, with small amounts of other gases.

Correct: (D)

NPK fertilisers contain all three essential elements: nitrogen, phosphorus and potassium.

Correct: (B)

Alkanes are saturated hydrocarbons with the general formula CnH2n+2.

Correct: (A)

Ethene reacts with bromine in an addition reaction across the C=C bond, decolourising the bromine water.

Correct: (C)

Oxidation of ethanol (for example by acidified potassium manganate(VII)) produces ethanoic acid.

Correct: (C)

In addition polymerisation, many unsaturated monomer molecules add together to form only the polymer.

Correct: (A)

Each fraction condenses at a different height in the column according to its boiling point range.

Correct: (D)

Hydrogen burns with a characteristic squeaky pop when a lighted splint is applied.

Correct: (B)

Rf = distance moved by the spot / distance moved by the solvent = 4.0 / 8.0 = 0.50.