GCSE Chemistry Practice Test 14

Correct: (C)

Almost all of the mass of an atom is in its nucleus, which contains protons and neutrons.

Correct: (A)

Electrons have a very small relative mass, about 1/1840, often treated as almost zero.

Correct: (D)

The group number equals the number of electrons in the outer shell, which is 7 for this element.

Correct: (B)

A full outer shell means noble gas atoms do not need to gain, lose or share electrons.

Correct: (D)

Newlands' pattern of properties repeating every eight elements only worked for the lightest elements and broke down beyond calcium.

Correct: (B)

Down the group the outer shell is further from the nucleus and more shielded, so the attraction for an incoming electron is weaker.

Correct: (A)

Chlorine is more reactive than bromine, so it displaces it: Cl2 + 2KBr → 2KCl + Br2.

Correct: (C)

Sodium reacts vigorously with water, producing hydrogen (fizzing) and sodium hydroxide, which is alkaline.

Correct: (A)

The metal loses electrons to form positive ions and the non-metal gains electrons to form negative ions.

Correct: (D)

The giant ionic lattice is held together by strong attractions in all directions, so lots of energy is needed to melt it.

Correct: (C)

C60 is a molecular form of carbon shaped like a hollow ball (similar to a football).

Correct: (B)

The forces between polymer chains are stronger than those between small molecules, so polymers are usually solid at room temperature.

Correct: (B)

The different-sized atoms disrupt the regular layers in an alloy, making it harder for the layers to slide.

Correct: (C)

The delocalised (free) electrons in a metal carry charge through the structure.

Correct: (A)

Diamond's hardness comes from its rigid three-dimensional network of strong covalent bonds.

Correct: (D)

Mr = 64 + 32 + (4 × 16) = 64 + 32 + 64 = 160.

Correct: (D)

Moles = mass / Mr = 100 / 100 = 1.0 mol.

Correct: (A)

Moles of H2 = 4 / 2 = 2 mol, so moles of H2O = 2 mol; mass = 2 × 18 = 36 g.

Correct: (B)

250 cm^3 = 0.25 dm^3, so concentration = 0.5 / 0.25 = 2 mol/dm^3.

Correct: (C)

Total Mr of reactants = 16 + 18 = 34; mass of desired product = 3 × 2 = 6; atom economy = (6 / 34) × 100 = 17.6%.

Correct: (C)

Volume = moles × 24 = 2.0 × 24 = 48 dm^3.

Correct: (B)

Yields are reduced by losses during filtration and transfer, incomplete reactions and unexpected side reactions.

Correct: (D)

Universal indicator is green at pH 7, red in strong acid and purple/blue in strong alkali.

Correct: (A)

Acid + alkali → salt + water: HCl + NaOH → NaCl + H2O.

Correct: (A)

Hydrogen ions are discharged at the cathode (negative electrode), giving hydrogen gas; oxygen forms at the positive electrode.

Correct: (C)

At the cathode the positive potassium ions gain electrons (reduction): K^+ + e^- → K.

Correct: (B)

Metals above carbon in the reactivity series cannot be extracted by carbon reduction, so electrolysis is used.

Correct: (D)

Zinc is more reactive than copper, so it displaces it: Zn + CuSO4 → ZnSO4 + Cu.

Correct: (B)

Oxidation Is Loss of electrons (OILRIG); reduction is the gain of electrons.

Correct: (D)

Opposite charges attract, so positive ions move to the negative cathode, where they gain electrons.

Correct: (C)

Thermal decomposition takes in energy from the surroundings to break compounds down, so it is endothermic.

Correct: (A)

Energy is transferred to the surroundings, so the products end up with less chemical energy than the reactants.

Correct: (C)

Energy to break bonds = 941 + (3 × 436) = 2249 kJ; energy released making bonds = 6 × 391 = 2346 kJ; ΔH = 2249 – 2346 = -97 kJ/mol.

Correct: (A)

A cell produces electricity by a chemical reaction; once a reactant is used up, the reaction stops.

Correct: (B)

Hydrogen is oxidised at the electrode in a controlled way, releasing electrical energy with water as the only product.

Correct: (D)

Mean rate = 120 / 40 = 3 cm^3/s.

Correct: (D)

At higher temperatures particles move faster, collide more often and a greater proportion of collisions exceed the activation energy.

Correct: (C)

More particles are exposed at the surface of a powder, increasing the frequency of collisions with the acid.

Correct: (A)

Compressing a gas pushes the particles closer together, raising the collision frequency.

Correct: (B)

At equilibrium both reactions continue at equal rates, so the amounts of reactants and products stay constant.

Correct: (A)

Catalysts affect both directions equally, so they change the time to reach equilibrium, not the position or yield.

Correct: (B)

Hydrocarbons contain only carbon and hydrogen atoms.

Correct: (D)

Bitumen contains the longest hydrocarbon molecules, so it has the highest boiling point and is used for road surfaces.

Correct: (C)

Incomplete combustion of hydrocarbons produces carbon monoxide, which is toxic because it reduces the blood's oxygen-carrying ability.

Correct: (B)

Hydration of ethene uses a phosphoric acid catalyst at about 300°C and 60-70 atmospheres pressure.

Correct: (A)

Like other acids, carboxylic acids release carbon dioxide from carbonates, which fizzes (effervesces).

Correct: (C)

In condensation polymerisation the monomer units join together and a small molecule, usually water, is lost for each bond formed.

Correct: (D)

Ink is a mixture of dyes that would run in the solvent; pencil (graphite) is insoluble and stays on the start line.

Correct: (D)

Oxygen relights a glowing splint; this is its standard test.

Correct: (B)

Barium sulfate is insoluble, so a white precipitate forms; the acid first removes carbonate ions that would also form a white precipitate.

Correct: (A)

Sodium ions give a strong yellow flame colour; potassium is lilac, lithium is crimson and copper is green.

Correct: (C)

The atmosphere is about 78% nitrogen and 21% oxygen, with about 0.9% argon and 0.04% carbon dioxide.

Correct: (A)

Algae first produced oxygen by photosynthesis about 2.7 billion years ago, and plants later increased it further.

Correct: (D)

Soot particles reflect sunlight (global dimming) and can damage the lungs when inhaled.

Correct: (B)

Renewable energy sources release little or no carbon dioxide, so using them reduces the carbon footprint.

Correct: (C)

Desalination removes dissolved salts by distillation or by reverse osmosis through membranes under pressure.

Correct: (B)

Bacteria break down low-grade ores and produce a leachate solution rich in metal ions, which can then be extracted.

Correct: (C)

Recycling conserves finite raw materials and uses less energy than producing glass from scratch.

Correct: (D)

NPK fertilisers supply nitrogen (N), phosphorus (P) and potassium (K), the elements plants need in largest amounts.

Correct: (A)

Because iron is below carbon in the reactivity series, carbon reduces iron oxide to iron; the carbon is itself oxidised.