IGCSE Chemistry Practice Test 1

Correct: (B)

Evaporation is the process in which particles with enough energy escape from the surface of a liquid to form a gas.

Correct: (D)

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

Correct: (A)

Gas particles move randomly and quickly in all directions, so they spread out and mix rapidly.

Correct: (C)

Number of neutrons = nucleon number – proton number = 23 – 11 = 12.

Correct: (A)

An electron has a relative mass of about 1/1840, much smaller than a proton or a neutron (relative mass 1).

Correct: (C)

Isotopes have the same proton number (so they are the same element) but different nucleon numbers because they contain different numbers of neutrons.

Correct: (D)

The first shell holds 2 electrons and the second shell holds 8, leaving 2 electrons in the third shell: 2,8,2.

Correct: (B)

Sodium loses its single outer electron to form a positive ion with a full outer shell.

Correct: (D)

Diamond is a giant covalent structure in which every carbon atom is covalently bonded to four other carbon atoms in a rigid network.

Correct: (A)

Magnesium loses two electrons to form Mg^2+ and oxygen gains two electrons to form O^2-, so both ions have full outer shells.

Correct: (B)

Carbon dioxide is formed between two non-metals and contains only shared pairs of electrons (covalent bonds).

Correct: (C)

Mr = 40 + 2 × (16 + 1) = 40 + 34 = 74.

Correct: (C)

Moles = mass / Mr = 8.0 / 16 = 0.50 mol.

Correct: (B)

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

Correct: (D)

Moles = 5.85 / 58.5 = 0.10 mol; concentration = 0.10 mol / 0.500 dm^3 = 0.20 mol/dm^3.

Correct: (A)

Moles in 100 g: C = 40.0 / 12 = 3.33, H = 6.7 / 1 = 6.7, O = 53.3 / 16 = 3.33. The ratio is 1 : 2 : 1, so the empirical formula is CH2O.

Correct: (A)

Percentage yield = (actual / theoretical) × 100 = (15 / 20) × 100 = 75%.

Correct: (D)

0.10 mol of carbon forms 0.10 mol of CO2, so mass = 0.10 × 44 = 4.4 g.

Correct: (C)

Hydrogen ions are discharged at the negative cathode in preference to sodium ions, forming hydrogen gas.

Correct: (B)

Cations are positively charged, so they are attracted to the negatively charged cathode.

Correct: (B)

Bromide ions lose electrons at the anode to form bromine; lead is formed at the cathode.

Correct: (A)

Hydrogen ions gain electrons at the cathode to form hydrogen gas.

Correct: (D)

The object to be plated is made the cathode, and the electrolyte must contain ions of the plating metal, Cu^2+.

Correct: (C)

Combustion releases energy to the surroundings as heat, so it is an exothermic process.

Correct: (C)

Energy absorbed breaking bonds = 436 + 242 = 678 kJ. Energy released forming bonds = 2 × 431 = 862 kJ. ΔH = 678 – 862 = -184 kJ/mol.

Correct: (D)

The temperature falls because the process takes in energy from the surroundings, so it is endothermic.

Correct: (A)

Energy = mass × specific heat capacity × temperature change = 100 × 4.2 × 10 = 4200 J.

Correct: (B)

In a fuel cell, hydrogen and oxygen combine to form water, and the energy released is converted directly into electricity.

Correct: (D)

Powdered marble has a much larger surface area, so collisions between particles happen more frequently and the rate increases.

Correct: (B)

A catalyst provides a different pathway with a lower activation energy, so a greater proportion of collisions are successful.

Correct: (C)

At a higher temperature the particles move faster, collide more frequently, and more of the collisions have enough energy for a reaction to occur.

Correct: (A)

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

Correct: (A)

Zinc is oxidised and copper(II) ions are reduced, so oxidation and reduction take place together.

Correct: (C)

Magnesium gains oxygen and loses electrons, so it is oxidised.

Correct: (B)

Average rate = volume of gas / time = 50 / 25 = 2 cm^3/s.

Correct: (D)

Sulfur dioxide is a non-metal oxide and is acidic; the others are metal oxides and are basic.

Correct: (B)

A pH of 2 is well below 7 and indicates a strongly acidic solution containing a high concentration of H^+ ions.

Correct: (D)

Potassium nitrate is a soluble salt of a Group I metal, so it is prepared by titrating potassium hydroxide with nitric acid; the other salts listed are insoluble.

Correct: (A)

Barium chloride gives a white precipitate of barium sulfate with sulfate ions; the acid is added first to remove carbonate ions, which would also form a precipitate.

Correct: (C)

Alkalis release ammonia gas when warmed with ammonium salts; this is the test for ammonium ions.

Correct: (C)

Mixing a solution containing Pb^2+ ions with one containing SO4^2- ions forms insoluble lead(II) sulfate as a precipitate, which is filtered off, washed and dried.

Correct: (A)

Alkalis are soluble bases that release hydroxide ions, OH^-, when dissolved in water.

Correct: (D)

The group number equals the number of electrons in the outer shell, which is why elements in a group have similar chemical properties.

Correct: (B)

Transition elements form coloured compounds, often have variable oxidation states, and are mostly good conductors with high melting points.

Correct: (D)

Down Group I the outer electron is further from the nucleus and is lost more easily, so reactivity increases.

Correct: (C)

Chlorine is a green gas, bromine is a red-brown liquid and iodine is a grey-black solid; reactivity decreases down the group.

Correct: (B)

In the reactivity series, potassium is near the top, well above zinc, iron and copper.

Correct: (A)

Aluminium quickly forms a tough oxide layer on its surface, which protects the metal underneath from further attack.

Correct: (A)

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

Correct: (B)

Experiments show that iron rusts only when both oxygen (from the air) and water are present.

Correct: (C)

Sulfur dioxide dissolves in rainwater to form an acidic solution; it is released when fossil fuels containing sulfur impurities are burned.

Correct: (D)

NPK fertilisers supply nitrogen, phosphorus and potassium, the three elements most needed for healthy plant growth.

Correct: (C)

Chlorine sterilises the water by killing harmful bacteria and other microorganisms; insoluble solids are removed earlier by filtration.

Correct: (D)

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

Correct: (B)

Ethene is unsaturated and contains a C=C double bond, so it reacts with bromine in an addition reaction and decolourises it.

Correct: (A)

Fermentation uses enzymes in yeast, works best when warm, and must take place without air (anaerobic conditions).

Correct: (B)

Carboxylic acids contain the -COOH group; for example, ethanoic acid is CH3COOH.

Correct: (A)

Many ethene molecules join together by addition polymerisation, and no other product is formed.

Correct: (D)

Hydrogen burns rapidly with a squeaky pop when a lighted splint is put into the gas.

Correct: (C)

Rf = distance moved by the dye / distance moved by the solvent = 5.0 / 10.0 = 0.50.