GCSE Chemistry Practice Test 1

Correct: (C)

Electrons are arranged in shells around the nucleus; they have a relative charge of -1 and a very small relative mass.

Correct: (B)

Number of neutrons = mass number – atomic number = 23 – 11 = 12.

Correct: (D)

Aluminium has 13 electrons: 2 in the first shell, 8 in the second and 3 in the third shell.

Correct: (A)

Isotopes have the same atomic number (protons) but different mass numbers because they contain different numbers of neutrons.

Correct: (B)

Magnesium is the Group 2 element in the third row (Period 3) of the periodic table.

Correct: (D)

Mendeleev left gaps for elements not yet discovered, and his predictions of their properties were later shown to be correct.

Correct: (A)

Noble gas atoms have a stable, full outer shell of electrons, so they do not need to gain, lose or share electrons.

Correct: (C)

Ar = (75 × 35 + 25 × 37) / 100 = (2625 + 925) / 100 = 35.5.

Correct: (B)

In a solid the ions are locked in a lattice and cannot move; when molten the ions are free to move and carry charge.

Correct: (A)

A covalent bond is a shared pair of electrons between two atoms.

Correct: (D)

Diamond has a giant covalent structure in which every carbon atom is bonded to four others, making it extremely hard.

Correct: (C)

Each carbon atom in graphite is bonded to three others, leaving one delocalised electron per atom that can carry charge.

Correct: (A)

Metallic bonding is the strong electrostatic attraction between positive ions and delocalised electrons.

Correct: (B)

Nanoparticles are between 1 nm and 100 nm in size, containing only a few hundred atoms.

Correct: (D)

Methane is a simple molecule; only weak intermolecular forces need to be overcome to boil it, so its boiling point is low.

Correct: (C)

Mr = 40 + 12 + (3 × 16) = 100.

Correct: (C)

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

Correct: (B)

Moles of CaCO3 = 5.0 / 100 = 0.050 mol, so moles of CO2 = 0.050; mass = 0.050 × 44 = 2.2 g.

Correct: (D)

250 cm^3 = 0.250 dm^3; concentration = 0.50 / 0.250 = 2.0 mol/dm^3.

Correct: (A)

Percentage yield = (36 / 45) × 100 = 80%.

Correct: (B)

Atom economy = (56 / 100) × 100 = 56%.

Correct: (C)

Volume = 0.25 × 24 = 6 dm^3.

Correct: (D)

A pH of 2 is well below 7, showing a strongly acidic solution with a high concentration of H^+ ions.

Correct: (A)

Acid + metal carbonate → salt + water + carbon dioxide.

Correct: (C)

Sulfuric acid forms sulfate salts; copper oxide + sulfuric acid → copper sulfate + water.

Correct: (B)

Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from the acid.

Correct: (A)

Copper is less reactive than hydrogen, so copper ions are discharged at the cathode and copper metal forms.

Correct: (D)

Bromide ions are discharged at the positive electrode, forming bromine. Lead forms at the negative electrode.

Correct: (C)

Hydrogen burns with a squeaky pop when a lit splint is held at the mouth of the tube.

Correct: (B)

Zinc is higher in the reactivity series, so it displaces copper: zinc + copper sulfate → zinc sulfate + copper.

Correct: (A)

Combustion releases energy to the surroundings, so it is exothermic; the others take in energy.

Correct: (D)

The activation energy is the minimum energy particles must have for a reaction to occur, measured from the reactant level to the top of the profile.

Correct: (C)

Energy to break bonds = 436 + 242 = 678 kJ; energy released forming bonds = 2 × 431 = 862 kJ; overall change = 678 – 862 = -184 kJ/mol.

Correct: (B)

In a hydrogen fuel cell hydrogen is oxidised to form water only: 2H2 + O2 → 2H2O.

Correct: (D)

A fall in temperature shows energy has been taken in from the surroundings, so the reaction is endothermic.

Correct: (B)

At higher temperatures particles move faster, collide more often and a greater proportion of collisions have enough energy to react.

Correct: (A)

A catalyst lowers the activation energy by providing a different pathway, and it is not used up.

Correct: (C)

Collecting the gas in a syringe or over water and recording the volume at regular intervals gives the rate of the reaction.

Correct: (D)

Mean rate = volume of gas / time = 90 / 30 = 3.0 cm^3/s.

Correct: (A)

At equilibrium the forward and reverse reactions continue at the same rate, so the concentrations stay constant. Equilibrium requires a closed system.

Correct: (C)

There are 4 moles of gas on the left and 2 moles on the right, so higher pressure favours the forward reaction, which produces fewer gas molecules.

Correct: (B)

Fractional distillation separates crude oil into fractions according to their different boiling points.

Correct: (D)

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

Correct: (A)

The C=C double bond in ethene opens up and bromine atoms add on, removing the orange colour of the bromine water.

Correct: (C)

With a plentiful supply of oxygen, a hydrocarbon burns completely to give carbon dioxide and water.

Correct: (B)

Ethene reacts with steam at high temperature and pressure, with a catalyst, to form ethanol (hydration).

Correct: (D)

In addition polymerisation the double bonds in many ethene monomers open up and join together to form the polymer; no other product is formed.

Correct: (A)

Pure substances melt and boil at specific temperatures; impurities lower the melting point and make it melt over a range.

Correct: (C)

Rf = distance moved by the dye / distance moved by the solvent = 6.0 / 15.0 = 0.40.

Correct: (B)

Chlorine bleaches damp litmus paper, turning it white.

Correct: (D)

Potassium compounds give a lilac flame in a flame test.

Correct: (C)

The atmosphere is about 78% nitrogen, 21% oxygen and small amounts of other gases including carbon dioxide.

Correct: (A)

Methane absorbs long wavelength radiation from the Earth and keeps the surface warm; carbon dioxide and water vapour are also greenhouse gases.

Correct: (D)

Carbon monoxide combines with haemoglobin in red blood cells, preventing oxygen from being transported around the body.

Correct: (B)

Sulfur dioxide dissolves in rainwater to form acid rain, which damages buildings, trees and aquatic life.

Correct: (D)

Fresh water is filtered to remove insoluble solids and then sterilised, for example with chlorine, to kill microbes.

Correct: (A)

In phytomining, plants take up metal compounds through their roots; the harvested plants are burned and the metal is extracted from the ash.

Correct: (B)

The Haber process uses a compromise temperature of about 450 °C, a pressure of 200 atmospheres and an iron catalyst.

Correct: (C)

An LCA assesses the environmental impact of every stage of a product's life, from obtaining raw materials to its final disposal.

Correct: (A)

Recycling aluminium uses far less energy than electrolysis of bauxite and conserves the ore and fossil fuels.