GCSE Chemistry Practice Test 17

Correct: (B)

Protons and neutrons are in the central nucleus; electrons are in shells around it.

Correct: (D)

An electron has a relative charge of -1 and a very small mass.

Correct: (A)

Isotopes have the same proton number, so they are the same element, but different neutron numbers.

Correct: (C)

Sodium has 11 electrons arranged as 2 in the first shell, 8 in the second and 1 in the third.

Correct: (B)

Group 1 metals become more reactive down the group because the outer electron is lost more easily.

Correct: (A)

A full outer shell makes noble gas atoms stable, so they do not easily gain, lose or share electrons.

Correct: (D)

Mass number = number of protons + number of neutrons in the nucleus.

Correct: (C)

Mendeleev left gaps and used patterns to predict properties of elements not yet discovered.

Correct: (A)

Ionic bonding involves electron transfer, producing oppositely charged ions that attract each other.

Correct: (C)

In a covalent bond, atoms share one or more pairs of electrons.

Correct: (D)

Diamond has a giant covalent structure with strong bonds throughout, making it very hard.

Correct: (B)

Metals consist of positive ions in a lattice with delocalised electrons moving through the structure.

Correct: (D)

In graphite, one electron from each carbon atom is delocalised and can carry charge.

Correct: (A)

Nanoparticles are very small, so a large proportion of their atoms are on the surface.

Correct: (C)

The strong covalent bonds inside molecules stay intact; weak forces between molecules are overcome during melting.

Correct: (B)

Moles = mass ÷ Mr = 4.0 ÷ 40 = 0.10 mol.

Correct: (A)

Mr = 40 + 12 + (3 × 16) = 100.

Correct: (D)

4.8 g Mg = 0.20 mol, which forms 0.20 mol MgO; mass = 0.20 × 40 = 8.0 g.

Correct: (C)

250 cm^3 = 0.250 dm^3, so concentration = 0.50 ÷ 0.250 = 2.0 mol/dm^3.

Correct: (B)

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

Correct: (D)

Atom economy = (136 ÷ 138) × 100 = 98.6%.

Correct: (A)

Volume = 0.25 × 24 = 6 dm^3.

Correct: (C)

Acids release hydrogen ions, H^+, when dissolved in water.

Correct: (B)

Alkalis are soluble hydroxides and produce hydroxide ions, OH^-, in aqueous solution.

Correct: (A)

Hydrochloric acid forms chloride salts, so magnesium oxide gives magnesium chloride.

Correct: (D)

At the cathode, positively charged lead ions gain electrons and form lead metal.

Correct: (C)

Potassium is near the top of the reactivity series and is more reactive than zinc, iron and copper.

Correct: (A)

Metal carbonates react with acids to form a salt, water and carbon dioxide.

Correct: (B)

Phenolphthalein is pink in alkaline solution and colourless in acidic solution.

Correct: (D)

In aqueous solution, hydrogen is produced at the cathode if the metal is more reactive than hydrogen.

Correct: (A)

Exothermic reactions release energy, usually raising the temperature of the surroundings.

Correct: (C)

Endothermic reactions take in energy, so the products have more energy than the reactants.

Correct: (B)

Breaking bonds is endothermic; energy must be supplied to break them.

Correct: (D)

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

Correct: (C)

The greater the difference in reactivity between the two electrodes, the greater the voltage produced.

Correct: (A)

Higher temperature gives particles more energy, causing more frequent and more successful collisions.

Correct: (D)

A catalyst lowers the activation energy and remains chemically unchanged at the end.

Correct: (B)

A higher concentration means more reacting particles per unit volume and more frequent collisions.

Correct: (C)

At equilibrium both reactions continue at equal rates, so concentrations stay constant.

Correct: (B)

There are 4 gas molecules on the left and 2 on the right, so higher pressure favours ammonia formation.

Correct: (A)

Increasing temperature favours the endothermic direction, which is the forward reaction here.

Correct: (D)

Fractional distillation separates hydrocarbons using their different boiling points.

Correct: (C)

Alkanes are saturated hydrocarbons with general formula CnH2n+2.

Correct: (A)

Ethene reacts with bromine in an addition reaction, decolourising bromine water.

Correct: (B)

Sugars are fermented by yeast in warm, anaerobic conditions to form ethanol and carbon dioxide.

Correct: (C)

Carboxylic acids contain the functional group -COOH.

Correct: (D)

Ethene molecules join together when their double bonds open, forming long polymer chains.

Correct: (B)

A pure substance melts and boils at specific temperatures; impurities change and broaden these ranges.

Correct: (A)

Substances spend different proportions of time in each phase, so they travel at different rates.

Correct: (D)

Rf = distance moved by dye ÷ distance moved by solvent = 4.0 ÷ 10.0 = 0.40.

Correct: (C)

Chlorine bleaches damp litmus paper, after first turning it red.

Correct: (B)

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

Correct: (D)

Combustion of coal, oil and natural gas releases carbon dioxide into the air.

Correct: (A)

Sulfur dioxide dissolves in rainwater to form acidic solutions, producing acid rain.

Correct: (C)

Carbon monoxide is toxic because it reduces the ability of blood to carry oxygen.

Correct: (D)

Sewage treatment reduces pollutants and microbes so the water can be released more safely.

Correct: (A)

Aluminium is too reactive to be extracted by carbon reduction, so electrolysis is used.

Correct: (C)

An LCA covers raw materials, manufacture, transport, use and disposal.

Correct: (B)

Recycling conserves ores and often reduces energy use and environmental damage.

Correct: (A)

Ammonia is manufactured using nitrogen and hydrogen at about 450°C and 200 atmospheres with an iron catalyst.