46 questions. Try each one, then open the answer to check yourself and read the explanation.
An element used in the production of matches is
Answer: D (sulphur.)
Match heads contain sulphur (with an oxidising agent such as potassium chlorate), which catches fire easily when struck.
In the diagram above, the respective activation energies for the catalyzed and uncatalyzed reactions in kJ are
Answer: C (30 and 35)
Activation energy = peak energy − energy of reactants. Reactants A + B are at 15 kJ; the catalysed peak is 45 kJ (45 − 15 = 30) and the uncatalysed peak is 50 kJ (50 − 15 = 35).
When calcium oxide is heated with carbon, the oxide will
Answer: A (be converted to the carbide)
In an electric furnace CaO + 3C → CaC2 + CO; calcium carbide is formed (it is later used to make ethyne).
A solution which on treatment with hydrochloric acid produces a colourless, odourless gas which turns lime water milky is most likely to be a
Answer: C (trioxocarbonate(IV))
Acids react with trioxocarbonates(IV) (carbonates) to release CO2, a colourless, odourless gas that turns lime water milky.
The soft solder used for welding and plumbing is an alloy of
Answer: A (lead and tin)
Soft solder is mainly lead and tin; the alloy melts at a low temperature, which makes it good for joining metals.
The reddish-brown rust on iron roofing sheets consists of
Answer: C (Fe2O3.3H2O)
Rust is hydrated iron(III) oxide, Fe2O3.xH2O, usually written Fe2O3.3H2O.
Na2S2O3(aq) + 2HCl(aq) → 2NaCl(aq) + H2O(l) + SO2(g) + S(s)
Which of the following would introduce the greatest increase in the rate of the chemical reaction above?
Answer: D (An increase in temperature and an increase in the concentration of the reactants.)
Raising the temperature and the concentration both make collisions more frequent and more energetic, so together they give the greatest increase in rate. Pressure has little effect because the reactants are in solution.
The tincture of iodine means iodine dissolved in
Answer: A (ethanol)
A tincture is a solution in alcohol; tincture of iodine is iodine dissolved in ethanol, used as an antiseptic.
Cu2+(aq) + 4NH3(g) ⇌ [Cu (NH3)4]2+(aq)
In the reaction above, what is the effect of precipitating Cu2+(aq) as CuS(s)?
Answer: B (More NH3(g) will be generated.)
By Le Chatelier's principle, removing a reactant (Cu2+) makes the equilibrium shift to the left to replace it, so the complex breaks up and more NH3 is produced.
Copper and silver metals are commonly used as coins because they are
Answer: D (not easily oxidized.)
Copper and silver are low in the activity series, so they do not easily react with air and water (are not easily oxidised) and coins stay intact.
Use the diagram below to answer questions 11 and 12.
The fuel gas labelled L is
Answer: A (water gas)
When air is blown over hot coke, producer gas forms; when steam (M) is blown over hot coke, water gas (CO + H2) is formed and leaves as L.
Use the diagram below to answer questions 11 and 12.
The alternative raw material labelled M is
Answer: B (steam)
Steam passed over red-hot coke gives water gas: C + H2O → CO + H2. So M is steam.
Which of the following sets of metals dissolves in dilute HCl?
Answer: C (Mg, Sn and Fe)
Metals above hydrogen in the activity series (Mg, Fe, Sn) displace hydrogen from dilute acid. Copper is below hydrogen, so any set with Cu is wrong.
H3PO4(aq) + H2O(l) ⇌ H2PO4−(aq) + H3O+(aq) ΔH = −13kJ at 298K
In the reaction above, an increase in temperature would
Answer: C (favour the reverse reaction)
The forward reaction is exothermic (ΔH negative), so heating favours the endothermic reverse reaction.
The reaction that takes place in a Daniell cell is
Answer: B (redox)
In a Daniell cell zinc is oxidised (Zn → Zn2+ + 2e−) while Cu2+ is reduced to copper, so the cell reaction is a redox reaction.
What happens when zinc rod is immersed in copper(II) tetraoxosulphate(VI) solution?
Answer: A (The blue colour of the solution disappears.)
Zinc displaces copper: Zn + Cu2+ → Zn2+ + Cu. As the blue Cu2+ ions are used up the solution loses its blue colour.
C2H4(g) + H2(g) → C2H6(g) ΔH = −137kJ mol−1
The reaction represented above is
Answer: A (exothermic)
A negative ΔH means heat is given out, so the reaction is exothermic.
How long would it take to deposit 0.08g of copper from CuCl2 solution by passing a current of 0.5A? [Cu = 64, F = 96500 C mol−1]
Answer: B (8 mins.)
Cu2+ + 2e− → Cu, so 64 g needs 2 × 96500 C. 0.08 g needs 0.08 × 193000/64 = 241.25 C. Time = 241.25 ÷ 0.5 = 482.5 s ≈ 8 minutes.
Tartaric acid is used industrially to
Answer: A (make baking powder)
Baking powder is a mixture of sodium hydrogencarbonate and tartaric acid; when wet, they react to give CO2, which makes dough rise.
The salt formed from a strong acid and a strong base is
Answer: B (neutral)
Neither ion of such a salt (e.g. NaCl) reacts with water, so its solution has pH 7: it is neutral.
Dissolving some pellets of NaOH in water would result in
Answer: D (an increase in the entropy of the solution.)
When solid NaOH dissolves, its ordered lattice breaks up into ions spread through the water, so the disorder (entropy) increases. The process gives out heat, so the temperature rises.
Calculate the number of moles of HCl present in 20 cm3 of a 0.75M solution of the acid.
Answer: A (0.015 mole)
Moles = concentration × volume in dm3 = 0.75 × 20/1000 = 0.015 mol.
The oxidation state of oxygen in tetraoxosulphate (VI) acid is
Answer: B (− 2)
Oxygen in H2SO4 has its usual oxidation state of −2: 2(+1) + 6 + 4(−2) = 0.
MnO2(s) + xHCl(aq) → MnCl2(aq) + yH2O(l) + zCl2(g)
In the equation above, what are the values of x, y, and z respectively?
Answer: C (4, 2, 1)
Balancing: MnO2 + 4HCl → MnCl2 + 2H2O + Cl2. Two O atoms need 2H2O, which needs 4H from 4HCl, and the 4 Cl give 2 in MnCl2 and 2 in Cl2.
Calculate the mass of chlorine gas which occupies a volume of 1.12 dm3 at s.t.p. [Cl=35.5, Molar volume of gas at s.t.p. = 22.4 dm3]
Answer: C (3.55 g)
Moles of Cl2 = 1.12/22.4 = 0.05 mol. Mass = 0.05 × 71 = 3.55 g.
Which experiment led to the measurement of the charge on an electron?
Answer: B (Oil-drop experiment.)
Millikan's oil-drop experiment measured the charge on a single electron.
What is the volume of oxygen required to burn completely 45 cm3 of methane at s.t.p.?
Answer: D (90.0 cm3)
CH4 + 2O2 → CO2 + 2H2O. By Gay-Lussac's law 1 volume of methane needs 2 volumes of oxygen: 2 × 45 = 90 cm3.
How many electrons are in the L shell of 3115P?
Answer: B (8)
Phosphorus has 15 electrons arranged 2, 8, 5. The L shell is the second shell, which holds 8.
If the electron configuration of an element is 1s22s22p5, how many unpaired electrons are there?
Answer: C (1)
Five electrons in the three 2p orbitals fill them as ↑↓, ↑↓, ↑, leaving one unpaired electron.
Which of the following decreases when a given mass of gas is compressed to half its initial volume?
Answer: B (Average intermolecular distance.)
Compressing a gas pushes the same number of molecules closer together, so the average distance between them falls; collisions actually become more frequent.
The elements that belong to the third period of the periodic table are
Answer: D (Na, Mg, S and Ar)
Period 3 runs from Na to Ar (Na, Mg, Al, Si, P, S, Cl, Ar). Li, Be, B, C, N and O are in period 2.
A metal X forms two bromides with the formulae XBr2 and XBr3. What type of bonding exists between X and bromine in the bromides?
Answer: A (Ionic bonding.)
X is a metal with variable valency (like iron); metals combine with halogens by transferring electrons, forming ionic (electrovalent) bonds.
A mixture of petrol and water can be separated through
Answer: C (the use of a separating funnel)
Petrol and water do not mix and form two layers, so the lower water layer can be run off using a separating funnel.
Which of the following represents an aromatic compound?
Answer: A (C6H5OH)
C6H5OH is phenol, which contains a benzene ring (C6H5−), so it is aromatic.
CH3CH2Cl + KCN → CH3CH2CN + KCl
In the reaction above, the cyanide is
Answer: C (nucleophilic)
The CN− ion has a lone pair and attacks the partly positive carbon, replacing Cl−. A species that seeks a positive centre is a nucleophile.
Which of the compounds is a tertiary alkanol?
Answer: C (CH3 — C(CH3)(OH) — CH2 — CH3)
In a tertiary alkanol the carbon bearing −OH is joined to three other carbons. In C that carbon carries two CH3 groups and a CH2CH3 group.
The hydrocarbon used in the production of styrene is
Answer: D (ethene.)
Benzene and ethene react to form ethylbenzene, which is dehydrogenated to styrene (C6H5CH=CH2).
The conversion of open chain alkanes into cycloalkanes and aromatic compounds is called
Answer: B (reforming)
Catalytic reforming turns straight-chain alkanes into ring compounds (cycloalkanes and aromatics) to improve petrol quality.
Which of the following alkanes has the highest boiling point?
Answer: A (Pentane.)
Boiling point rises with molecular size because van der Waals forces get stronger; pentane is the largest of the four.
Certain useful waxes are composed mainly of
Answer: D (alkanoates.)
Natural waxes are esters (alkanoates) formed from long-chain fatty acids and long-chain alcohols.
The IUPAC nomenclature of the compound CH3CH2COOCH2CH3 is
Answer: C (ethyl propanoate)
The acid part CH3CH2COO− has 3 carbons (propanoate) and the alcohol part −CH2CH3 is ethyl: ethyl propanoate.
When temporary hard water is boiled for some time in a kettle, the inner surface of the kettle becomes coated with a deposit of
Answer: B (calcium trioxocarbonate(IV))
Boiling decomposes dissolved Ca(HCO3)2 into insoluble CaCO3, CO2 and water; the CaCO3 forms the fur in the kettle.
A supersaturated solution is said to contain
Answer: D (more solute than it can dissolve at that temperature.)
A supersaturated solution holds more dissolved solute than a saturated solution at that temperature. It is unstable: a speck of undissolved solute makes the excess crystallise.
A good drying agent should be
Answer: C (hygroscopic)
A hygroscopic substance absorbs moisture from its surroundings without dissolving, so it can dry gases and other substances.
Smog usually occurs over cities which
Answer: A (burn a lot of fossil fuels)
Smog is smoke and fog mixed with pollutants (SO2, nitrogen oxides, soot) released mainly by burning fossil fuels.
What weight of NaCl is needed to make 2.0 dm3 of a 1.5M solution? [Na = 23, Cl = 35.5]
Answer: B (175 g)
Moles = 1.5 × 2.0 = 3.0 mol. Mass = 3.0 × 58.5 = 175.5 g ≈ 175 g.