GCSE Chemistry Practice Test 8

Correct: (C)

Neutrons = mass number – proton number = 14 – 6 = 8.

Correct: (D)

The proton number (atomic number) defines the element; atoms of an element can differ in neutrons and electrons.

Correct: (A)

17 electrons are arranged as 2 in the first shell, 8 in the second and 7 in the third shell.

Correct: (B)

Halogens react by gaining an electron; down the group the outer shell is further away and more shielded, so the attraction for an extra electron is weaker.

Correct: (D)

Thomson's plum pudding model had electrons dotted through a positively charged "pudding".

Correct: (A)

Relative atomic mass takes account of the abundance of each isotope: (75 × 35 + 25 × 37) / 100 = 35.5.

Correct: (C)

Potassium reacts very vigorously with water, forming potassium hydroxide and hydrogen.

Correct: (B)

Elements are ordered by increasing proton number, and this groups elements with similar properties together.

Correct: (A)

In ionic bonding, metal atoms lose electrons to form positive ions and non-metal atoms gain them to form negative ions.

Correct: (C)

Charged particles must be able to move for a substance to conduct; in the solid lattice the ions cannot move.

Correct: (B)

Fullerenes are molecules of carbon shaped as hollow balls or tubes, so other molecules can be trapped inside them.

Correct: (D)

Thermosoftening polymers have no cross-links, so heating overcomes the weak forces between chains and the polymer softens.

Correct: (C)

As particles get smaller their surface area to volume ratio increases hugely, giving more surface for reactions to occur on.

Correct: (A)

The delocalised electrons in metallic bonding can move and carry charge through the metal.

Correct: (B)

Every silicon and oxygen atom is joined by strong covalent bonds in a giant lattice, and there are no free electrons or ions.

Correct: (D)

Mr = (2 × 1) + 32 + (4 × 16) = 2 + 32 + 64 = 98.

Correct: (B)

Mass = moles × Mr = 2.5 × 40 = 100 g.

Correct: (C)

500 cm^3 = 0.5 dm^3; concentration = 20 / 0.5 = 40 g/dm^3.

Correct: (A)

A reaction stops when one reactant runs out; that reactant limits how much product can form.

Correct: (D)

Volume = 2 × 24 = 48 dm^3.

Correct: (B)

Losses in filtration or transfer, competing reactions and reversible reactions all reduce the amount of product collected.

Correct: (C)

Moles of HCl = 0.10 × (20.0 / 1000) = 0.002 mol, so moles of NaOH = 0.002; concentration = 0.002 / (25.0 / 1000) = 0.08 mol/dm^3.

Correct: (B)

Metal + acid → salt + hydrogen; here the salt is zinc chloride.

Correct: (D)

Insoluble salts are made by precipitation from two solutions containing the needed ions.

Correct: (A)

Copper is less reactive than hydrogen, so Cu^2+ ions are discharged at the cathode and pink-brown copper coats the electrode; oxygen forms at the anode.

Correct: (C)

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

Correct: (B)

Oxidation is the gain of oxygen (or the loss of electrons); reduction is the opposite.

Correct: (D)

pH 1 is strongly acidic, meaning the acid has ionised fully and there are many H^+ ions in the solution.

Correct: (A)

Alkalis release hydroxide ions in aqueous solution, which is what makes them alkaline.

Correct: (C)

Graphite conducts because of its delocalised electrons and is unreactive, so the electrodes are not consumed.

Correct: (D)

Dissolving ammonium nitrate takes in energy from the surroundings, so the temperature falls; combustion, neutralisation and respiration are exothermic.

Correct: (A)

Exothermic reactions release energy, so the surroundings get warmer.

Correct: (C)

Energy is needed to break bonds; when new bonds form, energy is given out.

Correct: (B)

ΔH = energy to break bonds – energy released making bonds = 500 – 650 = -150 kJ, so the reaction is exothermic.

Correct: (A)

The overall reaction in a hydrogen fuel cell is hydrogen + oxygen → water, so there are no polluting products in use.

Correct: (B)

Powder exposes far more surface, so acid particles collide with the surface more often and the rate increases.

Correct: (C)

A higher concentration means more particles per unit volume, giving more frequent collisions.

Correct: (D)

Equilibrium is dynamic: both reactions continue at the same rate, so there is no overall change.

Correct: (A)

Lower temperatures favour the exothermic direction, giving more ammonia at equilibrium, but the slower rate is why compromise temperatures are used.

Correct: (B)

As the reaction proceeds the reactants are used up, their concentration falls and the curve becomes less steep.

Correct: (C)

Higher pressure means the same number of particles in a smaller volume, so collisions are more frequent.

Correct: (D)

Bitumen is the thick residue with the longest chains; it is used for road surfaces and roofing.

Correct: (B)

Alkanes are saturated hydrocarbons (single bonds only) with the general formula CnH2n+2.

Correct: (A)

With a plentiful supply of oxygen, the carbon forms carbon dioxide and the hydrogen forms water.

Correct: (C)

The reaction ethene + steam ⇌ ethanol uses a phosphoric acid catalyst at high temperature and pressure (conditions differ from fermentation).

Correct: (D)

Vinegar is a dilute solution of ethanoic acid, a weak carboxylic acid.

Correct: (B)

DNA is made from nucleotide monomers; by comparison, proteins are made from amino acids and starch from glucose.

Correct: (C)

A pure substance contains one chemical, so it produces just one spot on the chromatogram.

Correct: (A)

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

Correct: (D)

Ba^2+ ions react with sulfate ions to give an insoluble white precipitate; the acid is added first to remove carbonate ions that would also give a white precipitate.

Correct: (B)

Oxygen is needed for burning, so it relights a splint that is glowing but has no flame.

Correct: (A)

Photosynthesis uses carbon dioxide and releases oxygen, which built up in the atmosphere over billions of years.

Correct: (D)

Sulfur dioxide (and nitrogen oxides) dissolve in rainwater to form acid rain, which damages buildings, trees and aquatic life.

Correct: (B)

Using renewables reduces the total greenhouse gas emissions caused over the product's life cycle.

Correct: (C)

Carbon particulates reflect sunlight back into space (global dimming) and can damage people's lungs.

Correct: (C)

Chlorine is used to sterilise drinking water; ozone and ultraviolet light are other sterilising methods.

Correct: (A)

Carbon and carbon monoxide are the reducing agents in the blast furnace; limestone is added to remove sandy impurities as slag.

Correct: (A)

Phytomining is a biological method of extraction used for low-grade ores, often of copper.

Correct: (D)

Nitrogen is extracted from air and hydrogen is produced from natural gas; they react over an iron catalyst to form ammonia.

Correct: (D)

Crude oil formed over millions of years and is being used up far faster than it can be replaced; wood, cotton and wool are renewable.