GCSE Chemistry Practice Test 10

Correct: (B)

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

Correct: (A)

Atoms have a radius of about 0.1 nm (1 × 10^-10 m).

Correct: (D)

8 electrons are arranged as 2 in the first shell and 6 in the second shell.

Correct: (C)

Chemical reactions depend on the arrangement of electrons, which is the same for all isotopes of an element.

Correct: (D)

With a full outer shell, noble gas atoms do not need to gain, lose or share electrons, so they are stable and unreactive.

Correct: (C)

Ar = (80 × 24 + 10 × 25 + 10 × 26) / 100 = (1920 + 250 + 260) / 100 = 24.3.

Correct: (A)

Transition metals form coloured compounds and many act as catalysts; they are hard, dense and far less reactive than Group 1 metals.

Correct: (B)

In Period 3, the Group 2 element is magnesium (sodium is Group 1 and aluminium is Group 3).

Correct: (A)

A covalent bond is a shared pair of electrons, usually formed between non-metal atoms.

Correct: (D)

When a simple molecular substance melts, only the weak forces between molecules are overcome; the strong covalent bonds within the molecules stay intact.

Correct: (B)

Silicon dioxide has a giant covalent structure, like diamond, with strong covalent bonds in all directions.

Correct: (C)

Fullerenes, such as buckminsterfullerene (C60), are carbon molecules shaped as hollow spheres or tubes.

Correct: (C)

Charge can only be carried if the ions are free to move to the electrodes, which happens in the liquid state or in solution.

Correct: (B)

Two F^- ions are needed to balance the charge of one Ca^2+ ion, giving CaF2.

Correct: (D)

Covalent cross-links between the chains stop thermosetting polymers from softening or melting on heating.

Correct: (A)

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

Correct: (B)

Mass = moles × Mr = 0.25 × 100 = 25 g.

Correct: (C)

The limiting reactant is the one that is completely used up, and it limits the amount of product that can form.

Correct: (A)

Volume = 500 cm^3 = 0.500 dm^3, so concentration = 10 / 0.500 = 20 g/dm^3.

Correct: (D)

Percentage yield = (13 / 20) × 100 = 65%.

Correct: (A)

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

Correct: (B)

Total Mr of all products = 28 + (3 × 2) = 34; atom economy = (6 / 34) × 100 = 17.6%.

Correct: (D)

Hydrochloric acid is a strong acid with a pH of about 1, so universal indicator turns red.

Correct: (C)

Sulfuric acid always forms salts called sulfates.

Correct: (D)

Oxygen is produced at the anode, while copper is deposited at the cathode.

Correct: (A)

Metals that are more reactive than carbon, such as aluminium, must be extracted by electrolysis of the molten compound.

Correct: (C)

Metal + acid → salt + hydrogen.

Correct: (B)

The indicator changes colour at the end point, showing the volume of acid needed for exact neutralisation.

Correct: (C)

Iron is more reactive than copper and displaces it, forming pink-brown copper and a pale green iron(II) sulfate solution as the blue colour fades.

Correct: (D)

Positive ions are attracted to the oppositely charged negative electrode, which is the cathode.

Correct: (B)

Thermal decomposition takes in energy from the surroundings and is endothermic; combustion, neutralisation and respiration are all exothermic.

Correct: (A)

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

Correct: (A)

The greater the difference in reactivity between the two metals used as electrodes, the greater the voltage of the cell.

Correct: (B)

Only collisions with energy equal to or greater than the activation energy result in bonds breaking and a reaction occurring.

Correct: (C)

In an endothermic reaction, energy is taken in from the surroundings, so the products sit higher on the energy profile than the reactants.

Correct: (D)

The rate can be followed by measuring how the volume of gas produced changes with time.

Correct: (D)

Powder exposes more particles to the acid, giving a much larger surface area and more frequent collisions.

Correct: (B)

Mean rate = volume of gas produced / time = 100 / 40 = 2.5 cm^3/s.

Correct: (A)

Hydrated copper sulfate ⇌ anhydrous copper sulfate + water is reversible, shown by the blue-white colour changes in each direction.

Correct: (C)

Raising the temperature favours the endothermic (reverse) reaction, so the equilibrium moves to the left and the yield of products falls.

Correct: (B)

A catalyst increases the rates of both the forward and reverse reactions by the same amount, so the position of equilibrium is unchanged.

Correct: (A)

Hydrocarbons are compounds whose molecules contain hydrogen and carbon atoms only.

Correct: (C)

Alkanes follow the general formula CnH2n+2, so propane (n = 3) is C3H8.

Correct: (D)

With a limited supply of oxygen, poisonous carbon monoxide is formed instead of carbon dioxide.

Correct: (C)

Carboxylic acids contain the -COOH functional group.

Correct: (D)

Ethene monomers add together by opening their C=C bonds, with no other product formed, so this is addition polymerisation.

Correct: (A)

Enzymes in yeast convert glucose into ethanol and carbon dioxide at about 30°C in the absence of oxygen.

Correct: (B)

Oxygen relights a glowing splint, which is the standard test for the gas.

Correct: (D)

Chlorine bleaches damp litmus paper white (the paper may turn red first, then bleach).

Correct: (A)

Barium chloride solution, after adding dilute hydrochloric acid, gives a white precipitate of barium sulfate if sulfate ions are present.

Correct: (B)

Carbonates react with dilute acids to release carbon dioxide, which turns limewater cloudy.

Correct: (C)

Photosynthesis by algae, and later by plants, released oxygen into the atmosphere over billions of years.

Correct: (A)

Carbon dioxide dissolved in the oceans and was locked away as carbonates in sedimentary rocks such as limestone, and in fossil fuels.

Correct: (C)

Sulfur dioxide and nitrogen oxides, formed when fossil fuels burn, dissolve in rainwater to form acid rain.

Correct: (D)

Particulates reflect sunlight back into space, causing global dimming, and they can damage the lungs and cause health problems.

Correct: (B)

Chlorine sterilises drinking water by killing microorganisms, making it safe to drink.

Correct: (B)

In bioleaching, bacteria convert insoluble metal compounds in low-grade ores into soluble compounds that leach out in a solution.

Correct: (D)

In the Haber process, nitrogen is obtained from the air and hydrogen is obtained mainly from natural gas.

Correct: (C)

In an alloy, atoms of a different size disrupt the regular layers of metal atoms, stopping the layers sliding and making the alloy harder.

Correct: (A)

Crude oil is a finite resource that took millions of years to form and will eventually run out.