GCSE Chemistry Practice Test 5

Correct: (B)

Electrons have a relative charge of -1 and a negligible mass (about 1/1836 of a proton).

Correct: (C)

Number of neutrons = mass number – atomic number = 23 – 11 = 12.

Correct: (A)

Magnesium is in Period 3 and Group 2; calcium is also Group 2 but is in Period 4.

Correct: (D)

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

Correct: (B)

Early tables ordered elements by relative atomic mass; the modern table uses atomic (proton) number.

Correct: (C)

The 17 electrons fill the shells as 2 in the first, 8 in the second and 7 in the third shell.

Correct: (A)

A full outer shell makes noble gas atoms stable, so they do not easily gain, lose or share electrons.

Correct: (D)

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

Correct: (C)

Metal atoms lose electrons to form positive ions and non-metal atoms gain them to form negative ions.

Correct: (D)

The electrostatic attractions between oppositely charged ions act in all directions, so a lot of thermal energy is needed to break them.

Correct: (B)

Every carbon atom is bonded to four others by strong covalent bonds, making the whole structure very rigid and hard.

Correct: (A)

Only the weak intermolecular forces between molecules need to be overcome to boil it, so the boiling point is low.

Correct: (C)

In a solid metal the delocalised electrons are free to move and carry the current, while the ions stay in place.

Correct: (D)

Nanoparticles measure between 1 nm and 100 nm and contain only a few hundred atoms.

Correct: (B)

The fourth outer electron of each carbon atom in graphite is delocalised and can move along the layers to carry charge.

Correct: (A)

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

Correct: (D)

12 g of carbon is 1 mol, which forms 1 mol of CO2 = 44 g.

Correct: (C)

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

Correct: (B)

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

Correct: (A)

atom economy = (56 / 100) × 100 = 56%.

Correct: (D)

volume = 0.25 × 24 = 6.0 dm^3.

Correct: (C)

Mass of oxygen = 4 × 16 = 64, so percentage = (64 / 98) × 100 = 65%.

Correct: (B)

Metals above hydrogen in the reactivity series react with dilute acids to give a salt and hydrogen.

Correct: (C)

Positive lead ions, Pb^2+, move to the negative cathode and are discharged as lead metal.

Correct: (A)

Soluble hydroxides and oxides that release OH^- ions in solution are called alkalis.

Correct: (D)

Strong acids are fully ionised in solution and have very low pH values, around 1.

Correct: (C)

Sulfuric acid always forms sulfate salts, so the product here is copper sulfate.

Correct: (B)

Potassium is near the top of the reactivity series and reacts violently with cold water; copper does not react at all.

Correct: (A)

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

Correct: (D)

Metals below carbon in the reactivity series can be extracted by reduction with carbon.

Correct: (A)

Exothermic reactions release energy, usually warming up the surroundings.

Correct: (B)

Energy used breaking bonds = 436 + 242 = 678 kJ; energy released making bonds = 2 × 431 = 862 kJ; overall change = 678 – 862 = -184 kJ/mol.

Correct: (C)

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

Correct: (D)

Hydrogen and oxygen combine to form only water, generating electricity.

Correct: (B)

The greater the difference in reactivity between the two electrodes, the greater the voltage produced.

Correct: (B)

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

Correct: (D)

At a higher temperature more particles have energy greater than the activation energy, so successful collisions are more frequent.

Correct: (B)

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

Correct: (C)

Increasing the temperature shifts the equilibrium in the endothermic (reverse) direction, so less ammonia is present at equilibrium.

Correct: (A)

There are 3 gas molecules on the left and only 2 on the right, so a higher pressure shifts the position of equilibrium to the right.

Correct: (B)

At higher pressure the same number of particles occupies a smaller volume, so the frequency of collisions increases.

Correct: (C)

The hydrocarbons have different boiling points and condense at different levels of the fractionating column.

Correct: (A)

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

Correct: (D)

Alkenes react with bromine by addition across the double bond, so the orange colour fades.

Correct: (C)

Yeast enzymes convert glucose into ethanol and carbon dioxide under anaerobic conditions.

Correct: (A)

Poly(ethene) forms when ethene monomers join by opening their double bonds, with no other product formed.

Correct: (B)

Carboxylic acids react with carbonates to give a salt, water and carbon dioxide, so the mixture fizzes.

Correct: (A)

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

Correct: (D)

Oxygen relights a glowing splint; this is its standard chemical test.

Correct: (C)

Sodium ions produce a persistent yellow flame colour.

Correct: (B)

Barium sulfate is insoluble, so a white precipitate of BaSO4 forms.

Correct: (D)

Nitrogen makes up about 78% of the atmosphere and oxygen about 21%.

Correct: (A)

Methane absorbs long-wave radiation and contributes to the greenhouse effect, as does carbon dioxide.

Correct: (B)

With a limited oxygen supply the carbon in the fuel is only partly oxidised, forming toxic carbon monoxide.

Correct: (C)

Intense volcanic activity released gases, mainly carbon dioxide, which formed the early atmosphere.

Correct: (A)

Chlorine sterilises the water by killing microbes that could cause disease.

Correct: (D)

The industrial Haber process runs at about 450°C and 200 atmospheres with an iron catalyst.

Correct: (C)

An LCA covers extracting raw materials, manufacture, use, and disposal or recycling.

Correct: (A)

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

Correct: (D)

Mining produces huge quantities of waste rock and dust, destroys habitats and leaves scars on the landscape – one reason recycling metals is preferred.