GCSE Chemistry Practice Test 11

Correct: (B)

11 protons means atomic number 11, which is sodium; the configuration 2,8,1 also places it in Group 1.

Correct: (C)

Number of neutrons = mass number – atomic number = 14 – 6 = 8.

Correct: (A)

Group 1 metals become more reactive down the group because the outer electron is further from the nucleus and is lost more easily.

Correct: (D)

Isotopes are atoms of the same element (same proton number) with different numbers of neutrons.

Correct: (B)

The group number equals the number of electrons in the outer shell, which explains why elements in a group react similarly.

Correct: (C)

The proton number never changes (12); forming a 2+ ion means losing 2 electrons, so 12 – 2 = 10 electrons.

Correct: (A)

Relative atomic mass = (35 × 75 + 37 × 25) / 100 = (2625 + 925) / 100 = 35.5.

Correct: (D)

Noble gases already have a full outer shell, so they do not need to gain, lose or share electrons.

Correct: (C)

Ionic compounds have giant lattices held by strong electrostatic forces, giving high melting points; the ions can only move (and carry charge) when molten or dissolved.

Correct: (A)

In diamond each carbon atom forms four covalent bonds, giving a rigid giant covalent structure.

Correct: (D)

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

Correct: (B)

When a simple molecular substance boils, only the weak forces between molecules are broken; the strong covalent bonds inside the molecules stay intact.

Correct: (C)

Nanoparticles are 1-100 nm in size, containing a few hundred atoms, and have a very high surface area to volume ratio.

Correct: (A)

Metals consist of a lattice of positive ions in a 'sea' of delocalised electrons, which also explains why metals conduct electricity.

Correct: (B)

C60 molecules are hollow spheres (cages) of 60 carbon atoms joined in hexagonal and pentagonal rings.

Correct: (B)

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

Correct: (C)

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

Correct: (A)

500 cm^3 = 0.5 dm^3, so concentration = 10 / 0.5 = 20 g/dm^3.

Correct: (D)

Percentage yield = (4.5 / 6.0) × 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 = 0.5 × 24 = 12 dm^3.

Correct: (C)

The limiting reactant is the one that is completely used up; since the acid is in excess, the magnesium limits how much product can form.

Correct: (A)

Strong acids are fully ionised and have low pH values, typically around pH 1.

Correct: (B)

Hydrochloric acid always forms chloride salts, so copper oxide + hydrochloric acid gives copper chloride and water.

Correct: (D)

Lead ions (Pb^2+) are positively charged, so they move to the negative cathode where they gain electrons and form lead metal.

Correct: (C)

In the reactivity series, potassium is near the top, well above zinc, iron and copper.

Correct: (B)

In every neutralisation, hydrogen ions from the acid react with hydroxide ions from the alkali to form water.

Correct: (A)

Sodium is too reactive, so hydrogen is discharged at the cathode; chloride ions are discharged as chlorine at the anode.

Correct: (D)

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

Correct: (C)

Metals more reactive than carbon cannot be extracted by reduction with carbon, so electrolysis must be used.

Correct: (B)

The temperature of the surroundings increases, so energy is being released by the reaction: it is exothermic.

Correct: (C)

Energy to break bonds = 436 + 243 = 679 kJ/mol. Energy released forming bonds = 2 × 432 = 864 kJ/mol. Overall change = 679 – 864 = -185 kJ/mol.

Correct: (A)

The activation energy is the minimum energy that colliding particles must have for a reaction to occur.

Correct: (D)

In a hydrogen fuel cell, hydrogen reacts with oxygen to form water only, producing electricity.

Correct: (B)

Thermal decomposition takes in energy from the surroundings to break down the compound; combustion, respiration and neutralisation are all exothermic.

Correct: (C)

Higher temperature gives particles more kinetic energy, causing more frequent collisions with enough energy to react.

Correct: (A)

A catalyst offers a different pathway needing less activation energy, and it is not used up in the reaction.

Correct: (D)

Mean rate = volume of gas produced / time = 40 / 20 = 2 cm^3/s.

Correct: (B)

There are 4 molecules of gas on the left and 2 on the right, so increasing the pressure shifts the equilibrium to the right, towards fewer gas molecules.

Correct: (C)

Breaking a solid into smaller pieces increases its surface area to volume ratio, exposing more particles to collisions.

Correct: (A)

Heating drives the water out of hydrated copper sulfate, leaving white anhydrous copper sulfate; adding water reverses the change.

Correct: (D)

Hydrocarbons with different chain lengths have different boiling points, so they condense at different levels of the fractionating column.

Correct: (B)

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

Correct: (C)

Alkenes are unsaturated and react with bromine water in an addition reaction, turning it from orange to colourless.

Correct: (A)

Fermentation by yeast works best in warm, anaerobic (no oxygen) conditions, producing ethanol and carbon dioxide.

Correct: (D)

Cracking breaks long, less useful hydrocarbons into shorter alkanes (better fuels) and alkenes (used to make polymers).

Correct: (B)

Ethene is the monomer; many ethene molecules join together (opening their double bonds) to form the polymer chain.

Correct: (A)

Oxygen relights a glowing splint; the other tests identify hydrogen, carbon dioxide and chlorine respectively.

Correct: (C)

Rf = distance moved by the spot / distance moved by the solvent = 4.0 / 10.0 = 0.4.

Correct: (D)

Lithium compounds give a crimson-red flame; sodium gives yellow, potassium lilac and copper(II) green.

Correct: (B)

Carbonates react with acids to give carbon dioxide, and carbon dioxide turns limewater cloudy.

Correct: (C)

Intense volcanic activity produced an early atmosphere consisting mainly of carbon dioxide, with little or no oxygen.

Correct: (A)

The modern atmosphere is about 78% nitrogen, 21% oxygen, and small amounts of other gases including argon and carbon dioxide.

Correct: (D)

Sulfur dioxide dissolves in rainwater to form acidic solutions, producing acid rain that damages buildings and trees.

Correct: (B)

Methane absorbs long-wavelength radiation from the Earth and is a greenhouse gas, like carbon dioxide and water vapour.

Correct: (D)

Seawater contains too many dissolved salts, so they must be removed by desalination; filtration and chlorine alone cannot do this.

Correct: (C)

The Haber process (450 °C, 200 atmospheres) uses an iron catalyst to speed up the reversible reaction.

Correct: (B)

Phytomining uses plants to 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 considers extracting and processing raw materials, manufacture, use, and disposal, including transport and energy at each stage.

Correct: (B)

Recycling aluminium uses a fraction of the energy needed for extraction by electrolysis, saving finite ores and reducing emissions.