GCSE Chemistry Practice Test 2

Correct: (A)

Protons are found in the nucleus and have a relative mass of 1 and a relative charge of +1.

Correct: (C)

Mass number = number of protons + number of neutrons = 6 + 6 = 12.

Correct: (B)

Chlorine has 17 electrons: 2 in the first shell, 8 in the second and 7 in the third shell.

Correct: (D)

Down Group 1 the outer electron is further from the nucleus and is lost more easily, so the metals become more reactive.

Correct: (B)

Transition metals form coloured compounds, often have ions with different charges and are widely used as catalysts.

Correct: (A)

Chlorine is higher in Group 7, so it displaces the less reactive bromine from its compound, forming orange bromine.

Correct: (C)

Sodium loses its single outer electron to gain a full outer shell, forming an Na^+ ion.

Correct: (D)

Ar = (75 × 24 + 25 × 26) / 100 = (1800 + 650) / 100 = 24.5.

Correct: (A)

Water consists of simple molecules; boiling only overcomes the weak forces between molecules, not the strong covalent bonds within them.

Correct: (C)

Silicon dioxide is a giant covalent (macromolecular) structure, so a large amount of energy is needed to break its many strong covalent bonds.

Correct: (B)

In an alloy, atoms of different sizes disrupt the regular layers, preventing them from sliding over each other.

Correct: (D)

C60 is a fullerene: its carbon atoms are arranged in a hollow sphere of rings.

Correct: (A)

In the solid the ions are held in fixed positions in the lattice; when molten they can move to the electrodes.

Correct: (C)

There are no charged particles free to move in simple molecular substances, so they cannot carry an electric current.

Correct: (B)

Thermosoftening polymers have long chains held together only by weak intermolecular forces, with no cross-links, so they melt on heating.

Correct: (D)

Mr = (2 × 1) + 32 + (4 × 16) = 98.

Correct: (A)

Moles = mass / Mr = 11 / 44 = 0.25 mol.

Correct: (C)

Moles of CaCO3 = 10.0 / 100 = 0.10 mol, so moles of CO2 = 0.10; mass = 0.10 × 44 = 4.4 g.

Correct: (B)

500 cm^3 = 0.500 dm^3; concentration = 10 / 0.500 = 20 g/dm^3.

Correct: (A)

Moles = concentration × volume in dm^3 = 0.100 × 0.0250 = 0.00250 mol.

Correct: (D)

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

Correct: (B)

It is an addition-type reaction with a single product, so every atom of the reactants is incorporated into the ammonia.

Correct: (D)

A pH well above 7 shows an alkaline solution containing OH^- ions.

Correct: (A)

Excess insoluble base ensures all the acid reacts; filtering removes the unreacted base and crystallisation gives pure salt crystals.

Correct: (D)

Strong acids ionise completely in water; weak acids, such as ethanoic acid, ionise only partially.

Correct: (B)

Hydrogen forms at the cathode (sodium is too reactive), chlorine at the anode, and sodium hydroxide is left in solution.

Correct: (A)

Metals above carbon in the reactivity series, like aluminium, must be extracted by electrolysis because carbon cannot displace them from their oxides.

Correct: (C)

OILRIG: Oxidation Is Loss of electrons, Reduction Is Gain of electrons.

Correct: (D)

Iron is below carbon in the reactivity series, so carbon removes the oxygen from iron oxide in the blast furnace.

Correct: (B)

Metal + acid → salt + hydrogen, so magnesium + hydrochloric acid gives magnesium chloride and hydrogen.

Correct: (C)

Energy to break bonds = 436 + 193 = 629 kJ; energy released forming bonds = 2 × 366 = 732 kJ; overall change = 629 – 732 = -103 kJ/mol.

Correct: (A)

In an exothermic reaction energy is given out, so the products have less energy than the reactants.

Correct: (D)

In non-rechargeable cells the reaction cannot be reversed by passing a current; in rechargeable cells it can.

Correct: (B)

Energy = mass × specific heat capacity × temperature change = 50 × 4.2 × 10 = 2100 J (2.1 kJ).

Correct: (A)

Hydrogen is a gas that must be stored under pressure in strong tanks; its only combustion product is water, but storage is a major problem.

Correct: (D)

Powdering increases the surface area exposed to the acid, increasing the frequency of collisions and the rate of reaction.

Correct: (C)

The gradient of a volume-time graph represents the rate, so the steepest starting gradient is the fastest reaction.

Correct: (B)

A higher concentration means more particles in the same volume, so collisions between particles occur more often.

Correct: (A)

The forward reaction is exothermic so lower temperatures favour yield, but very low temperatures make the reaction too slow; 450 °C is a compromise.

Correct: (B)

Ammonium chloride splits into ammonia and hydrogen chloride when heated, and the two gases recombine to form ammonium chloride again when cooled.

Correct: (D)

Mean rate = volume of gas / time = 100 / 25 = 4.0 cm^3/s.

Correct: (B)

The shortest hydrocarbons with the lowest boiling points, the refinery gases (LPG), rise to the top of the column where it is coolest.

Correct: (A)

Cracking breaks long-chain alkanes into shorter, more useful alkanes and alkenes using high temperatures and a catalyst (or steam).

Correct: (C)

Alkenes contain one C=C double bond and have the general formula CnH2n.

Correct: (D)

Carboxylic acids react with carbonates in the same way as other acids, producing a salt, water and carbon dioxide.

Correct: (B)

Esters are formed when an alcohol reacts with a carboxylic acid, in the presence of an acid catalyst; ethanol + ethanoic acid gives ethyl ethanoate and water.

Correct: (A)

Condensation polymerisation involves functional groups reacting together, eliminating a small molecule such as water for each bond formed, as in polyesters.

Correct: (D)

Oxygen relights a glowing wooden splint held in the gas.

Correct: (C)

Sulfate ions react with barium chloride solution (after acidifying) to form a white precipitate of barium sulfate.

Correct: (A)

Copper(II) ions form a blue precipitate of copper(II) hydroxide with sodium hydroxide solution.

Correct: (B)

Distance moved by dye = Rf × distance moved by solvent = 0.60 × 20.0 = 12.0 cm.

Correct: (C)

Gases released by volcanoes made the early atmosphere rich in carbon dioxide, with water vapour and small amounts of other gases, similar to Mars and Venus today.

Correct: (A)

Photosynthesis by algae and later plants released oxygen and removed carbon dioxide from the atmosphere.

Correct: (D)

Microorganisms in the guts of cattle and in flooded rice fields release methane, a powerful greenhouse gas.

Correct: (B)

Particulates reflect sunlight, causing global dimming, and when inhaled they can cause respiratory and cardiovascular problems.

Correct: (C)

Desalination removes dissolved salts, either by distillation or by reverse osmosis through membranes under pressure; both need a lot of energy.

Correct: (B)

Sewage treatment includes screening, sedimentation and aerobic digestion by microorganisms before the water is released back into the environment.

Correct: (C)

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

Correct: (D)

Ammonia is converted into fertilisers such as ammonium nitrate, which supply nitrogen to crops.

Correct: (C)

During electrolysis, copper dissolves from the impure anode and pure copper is deposited on the cathode.