GCSE Chemistry Practice Test 9

Correct: (A)

Mass number = protons + neutrons = 11 + 12 = 23.

Correct: (B)

Neutrons are neutral; protons are positive and electrons are negative.

Correct: (C)

12 electrons are arranged as 2 in the first shell, 8 in the second and 2 in the third: 2,8,2.

Correct: (D)

Isotopes have the same number of protons but different numbers of neutrons.

Correct: (C)

Ar = (75 × 35 + 25 × 37) / 100 = (2625 + 925) / 100 = 35.5.

Correct: (A)

Reactivity increases down Group 1 because the outer electron is further from the nucleus and is lost more easily.

Correct: (D)

Mendeleev left gaps for undiscovered elements and correctly predicted their properties.

Correct: (B)

The number of electrons in the outer shell is 7, which gives the group number.

Correct: (B)

In ionic bonding, electrons are transferred from metal atoms to non-metal atoms, forming positive and negative ions.

Correct: (D)

Losing one negative electron leaves the ion with a single positive charge: Na^+.

Correct: (A)

Each carbon atom in diamond forms four strong covalent bonds in a giant covalent structure.

Correct: (C)

Each carbon atom in graphite bonds to only three others, leaving one delocalised electron per atom that can carry charge.

Correct: (D)

Ionic compounds have giant structures with strong electrostatic attractions in all directions, which need large amounts of energy to break.

Correct: (C)

Nanoparticles are between 1 and 100 nm in size and contain only a few hundred atoms.

Correct: (B)

Metals consist of a lattice of positive ions surrounded by delocalised electrons, and the attraction between them is the metallic bond.

Correct: (A)

Mr = 40 + 12 + (3 × 16) = 100.

Correct: (A)

Moles = mass / Mr = 8 / 40 = 0.2 mol.

Correct: (D)

Moles of CaCO3 = 5.0 / 100 = 0.05 mol, so moles of CO2 = 0.05 mol; mass = 0.05 × 44 = 2.2 g.

Correct: (C)

Concentration = moles / volume in dm^3 = 0.50 / 0.250 = 2.0 mol/dm^3.

Correct: (B)

Percentage yield = (30 / 40) × 100 = 75%.

Correct: (B)

Atom economy = (Mr of desired product / total Mr of all products) × 100 = (56 / 100) × 100 = 56%.

Correct: (A)

Volume = moles × 24 = 0.50 × 24 = 12 dm^3.

Correct: (D)

Neutral solutions have a pH of 7; acids are below 7 and alkalis are above 7.

Correct: (C)

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

Correct: (C)

Sodium is more reactive than hydrogen, so hydrogen ions are discharged at the cathode and hydrogen gas forms.

Correct: (B)

Zinc is more reactive than copper, so zinc displaces copper from the solution; copper metal forms and the blue colour fades.

Correct: (A)

Hydrochloric acid forms chloride salts, so the salt is sodium chloride.

Correct: (D)

Pb^2+ ions are positive, so they are attracted to the negative cathode, where they gain electrons and form lead atoms.

Correct: (D)

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

Correct: (A)

The mixture is filtered to remove the unreacted solid copper oxide before the filtrate is crystallised.

Correct: (C)

Exothermic reactions transfer energy to the surroundings, so the temperature of the surroundings rises.

Correct: (B)

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

Correct: (A)

Particles must collide with at least the activation energy for bonds to break and a reaction to take place.

Correct: (C)

In a hydrogen fuel cell, hydrogen reacts with oxygen and the only product is water.

Correct: (B)

The reaction takes in energy from the surroundings, so their temperature falls; this is an endothermic reaction.

Correct: (D)

Higher temperature gives particles more energy, so collisions are more frequent and a greater proportion of them are successful.

Correct: (B)

A catalyst lowers the activation energy by providing a different pathway, and it is not used up in the reaction.

Correct: (D)

Mean rate = volume of gas produced / time = 60 / 30 = 2.0 cm^3/s.

Correct: (C)

At equilibrium in a closed system, the forward and reverse reactions take place at exactly the same rate.

Correct: (A)

Higher pressure favours the side with fewer gas molecules, because this lowers the pressure again.

Correct: (C)

A higher concentration means more particles per unit volume, so they collide more often.

Correct: (A)

Crude oil is separated by fractional distillation, which uses the different boiling points of the hydrocarbons.

Correct: (B)

Alkanes are saturated hydrocarbons with the general formula CnH2n+2.

Correct: (D)

Alkenes contain a C=C double bond, which reacts with bromine and decolourises bromine water; alkanes do not.

Correct: (D)

An ester takes its first name from the alcohol (ethyl) and its second name from the acid (ethanoate), giving ethyl ethanoate.

Correct: (B)

In addition polymerisation, the C=C bonds in the monomers open up and the molecules join to form only the polymer.

Correct: (A)

Cracking breaks long-chain alkanes into shorter alkanes and alkenes, which are in greater demand.

Correct: (C)

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

Correct: (A)

Carbon dioxide turns limewater milky, which is the standard test for the gas.

Correct: (D)

Lithium compounds produce a crimson red flame in a flame test.

Correct: (B)

Rf = distance moved by the spot / distance moved by the solvent = 4.0 / 8.0 = 0.5.

Correct: (C)

Intense volcanic activity released gases, so the early atmosphere was mostly carbon dioxide, with little or no oxygen.

Correct: (B)

Air is about 78% nitrogen and about 21% oxygen, with small amounts of other gases.

Correct: (C)

Methane and carbon dioxide are greenhouse gases; they absorb infrared radiation and help to keep the Earth warm.

Correct: (D)

Carbon monoxide is toxic because it combines with haemoglobin, preventing it from carrying oxygen around the body.

Correct: (A)

Filtration, for example through sand beds, removes insoluble solids; sterilisation is then used to kill microbes.

Correct: (C)

In phytomining, plants absorb metal compounds from low-grade ores; the plants are harvested and burned, and the metal is extracted from the ash.

Correct: (D)

An LCA assesses the environmental impact of obtaining raw materials, manufacture, use and disposal of a product.

Correct: (A)

The Haber process uses an iron catalyst, at about 450°C and 200 atmospheres pressure.

Correct: (B)

Recycling saves energy, reduces waste and conserves finite metal ores.