GCSE Chemistry Practice Test 7

Correct: (B)

The proton number (17) decides the element; 17 protons is chlorine.

Correct: (A)

Isotopes have identical proton numbers but different neutron numbers, so their mass numbers differ.

Correct: (C)

12 electrons fill the shells as 2 in the first, 8 in the second and 2 in the third shell.

Correct: (D)

A full outer shell is a stable arrangement, so noble gases do not easily gain, lose or share electrons.

Correct: (B)

Protons = mass number – neutrons = 23 – 12 = 11.

Correct: (C)

Down the group the outer electron is shielded more and further away, so less energy is needed to remove it.

Correct: (A)

Alpha scattering experiments showed atoms are mostly empty space with a tiny, dense, positive nucleus.

Correct: (D)

Transition metals are typical hard, dense metals and many of their compounds are coloured; Group 1 metals are soft and form white compounds.

Correct: (C)

Sodium chloride is a giant lattice of Na^+ and Cl^- ions held together by electrostatic attraction.

Correct: (A)

The ionic bonds act in all directions throughout the giant lattice and need a lot of thermal energy to break.

Correct: (D)

The delocalised electrons are free to move through the structure and carry charge to the electrodes.

Correct: (B)

The four strong covalent bonds per atom in a 3D lattice make diamond very hard and give it a very high melting point.

Correct: (A)

Nanoparticles are 1-100 nm, so they may pass into cells; their long-term effects are still being studied.

Correct: (C)

In metallic bonding the positive ions sit in layers in a sea of delocalised electrons, and the layers can slide.

Correct: (D)

Boiling a molecular substance only separates the molecules, which takes little energy because intermolecular forces are weak.

Correct: (B)

Mr = 40 + 12 + (3 × 16) = 100.

Correct: (D)

Moles = mass / Mr = 8 / 16 = 0.5 mol.

Correct: (A)

Moles of Mg = 12 / 24 = 0.5 mol, so 0.5 mol of MgO forms; mass = 0.5 × 40 = 20 g.

Correct: (C)

250 cm^3 = 0.25 dm^3; concentration = 0.5 / 0.25 = 2.0 mol/dm^3.

Correct: (B)

Percentage yield = (32 / 40) × 100 = 80%.

Correct: (D)

Atom economy = 44 / (44 + 2 × 18) × 100 = 44 / 80 × 100 = 55%.

Correct: (A)

Volume = 0.25 × 24 = 6 dm^3.

Correct: (C)

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

Correct: (A)

Filtration removes unreacted oxide; the pure salt is then obtained by evaporation or crystallisation.

Correct: (D)

Hydrogen forms at the cathode because sodium is too reactive to be discharged; chloride ions give chlorine at the anode.

Correct: (B)

Calcium is reactive enough to react with cold water; copper and silver do not react, and iron only reacts very slowly with steam.

Correct: (C)

The thin, tough oxide coating forms instantly in air and stops the metal below from reacting further.

Correct: (A)

Pb^2+ ions are attracted to the negative electrode, gain electrons and form lead metal.

Correct: (D)

Acid strength describes the proportion of molecules that ionise, not the concentration.

Correct: (B)

Hydrogen ions from the acid react with hydroxide ions from the alkali to form water.

Correct: (A)

Combustion transfers energy to the surroundings, so the temperature rises; the others take in energy.

Correct: (C)

Activation energy is the energy barrier that colliding particles must overcome for a reaction to happen.

Correct: (B)

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

Correct: (D)

The further apart the two metals are in the reactivity series, the greater the voltage of the cell.

Correct: (C)

In the fuel cell hydrogen reacts with oxygen to produce water, releasing electrical energy.

Correct: (D)

Mean rate = volume / time = 60 / 30 = 2 cm^3/s.

Correct: (B)

At higher temperatures particles move faster, collide more frequently and more of them have at least the activation energy.

Correct: (A)

A catalyst lowers the activation energy and is not used up in the reaction.

Correct: (C)

Increasing pressure shifts equilibrium to the side with fewer molecules of gas, which is the ammonia side.

Correct: (D)

Recording gas volume against time lets you calculate the rate and plot a graph of the results.

Correct: (B)

Raising the temperature favours the endothermic direction (the reverse reaction), so less ammonia is formed at equilibrium.

Correct: (A)

Longer chains have higher boiling points, so each fraction condenses at a different height in the column.

Correct: (C)

Alkenes are unsaturated hydrocarbons with a C=C double bond and the general formula CnH2n.

Correct: (B)

Alkenes react with bromine in an addition reaction, removing its orange colour; alkanes do not.

Correct: (D)

Cracking breaks long chains into shorter, more useful alkanes and reactive alkenes.

Correct: (A)

Yeast respires anaerobically, converting glucose to ethanol and carbon dioxide.

Correct: (C)

Addition polymers are named after their monomer; poly(ethene) is made from many ethene molecules joining at their double bonds.

Correct: (B)

Rf = distance moved by substance / distance moved by solvent = 4 / 10 = 0.4.

Correct: (D)

Chlorine is a bleach, so it turns damp litmus paper white (it may turn it red first).

Correct: (A)

Sodium ions give an intense yellow flame; potassium gives lilac and calcium gives orange-red.

Correct: (C)

Carbonates react with acids to give carbon dioxide, which turns limewater milky.

Correct: (C)

Nitrogen is roughly four-fifths of the air and oxygen roughly one-fifth; other gases make up about 1%.

Correct: (A)

Methane (like carbon dioxide and water vapour) absorbs infrared radiation and keeps the Earth warm.

Correct: (D)

Intense volcanic activity released gases such as carbon dioxide, nitrogen, water vapour, methane and ammonia.

Correct: (B)

Carbon monoxide is a colourless, odourless toxic gas produced by incomplete combustion.

Correct: (B)

Filtering removes insoluble solids and sterilising kills microbes, making the water safe to drink.

Correct: (D)

Aluminium is too reactive to be extracted by carbon, so electrolysis is used; cryolite lowers the melting point of the mixture.

Correct: (C)

An LCA covers extracting and processing raw materials, manufacturing, use, transport and final disposal.

Correct: (A)

These are compromise conditions that give a reasonable yield at a reasonable rate and cost.

Correct: (B)

Recycling saves raw materials and energy and reduces mining and waste.