48 questions. Try each one, then open the answer to check yourself and read the explanation.
Sieving is a technique used to separate mixtures containing solid particles of
Answer: C (different sizes)
A sieve lets small particles through and holds back bigger ones, so it can only separate solids whose particle sizes are different.
Which of the following compounds is composed of Al, Si, O and H?
Answer: C (Clay)
Clay is hydrated aluminium silicate, e.g. Al2Si2O5(OH)4, which contains Al, Si, O and H. Epsom salt is MgSO4·7H2O, limestone is CaCO3 and urea is CO(NH2)2.
50 cm3 of carbon (II) oxide was exploded with 150 cm3 of air containing 20% oxygen by volume. Which of the reactants was in excess?
Answer: C (Oxygen)
2CO + O2 → 2CO2, so 50 cm3 of CO needs only 25 cm3 of O2. The air holds 20% × 150 = 30 cm3 of O2, so oxygen is in excess.
How many moles of HCl will be required to react with potassium heptaoxodichromate (VI) to produce 3 moles of chlorine?
Answer: A (14)
K2Cr2O7 + 14HCl → 2KCl + 2CrCl3 + 7H2O + 3Cl2, so 14 moles of HCl give 3 moles of chlorine.
The ratio of the initial to the final pressure of a given mass of gas is 1:1.5. Calculate the final volume of the gas if the initial volume was 300 cm3 at the same temperature.
Answer: B (200 cm3)
Boyle's law: P1V1 = P2V2, so 1 × 300 = 1.5 × V2 and V2 = 200 cm3.
The partial pressure of oxygen in a sample of air is 452 mm Hg and the total pressure is 780 mm Hg. What is the mole fraction of oxygen?
Answer: B (0.579)
Mole fraction = partial pressure ÷ total pressure = 452 ÷ 780 = 0.579.
The fundamental difference between the three states of matter is the
Answer: D (degree of movement of their particles)
Solids, liquids and gases are made of the same kind of particles; they differ in how freely the particles move (and how strongly they are held).
Which of the following statements is correct about the periodic table?
Answer: B (The valence electrons of the elements in the same period increase progressively across the period)
Across a period one electron is added to the outer shell at each step, so the number of valence electrons rises. Non-metallic character increases, not decreases, across a period.
The electron configuration of 22X2+ ion is
Answer: D (1s22s22p63s23p64s2)
The ion X2+ has 22 − 2 = 20 electrons, and D is the only option with 20 electrons. (Strictly, a transition metal loses its 4s electrons first, giving 1s22s22p63s23p63d2, but that is not offered.)
Which of the following types of bonding does not involve the formation of new substance?
Answer: A (Metallic)
Metallic bonding holds atoms of the same metal together; no new compound is formed. Covalent, co-ordinate and electrovalent bonds join atoms into new substances.
The knowledge of half-life can be used to
Answer: B (detect an element)
Each radioactive isotope has its own fixed half-life, so measuring the half-life helps to identify (detect) the element.
The shapes of CO2, H2O and CH4 respectively are
Answer: C (linear, bent and tetrahedral)
CO2 has no lone pairs on carbon, so it is linear; the two lone pairs on oxygen make H2O bent; CH4 has four bond pairs, so it is tetrahedral.
The distance between the nuclei of chlorine atoms in a chlorine molecule is 0.194 mm. The atomic radius of chlorine atom is
Answer: A (0.097 mm)
The atomic (covalent) radius is half the distance between the two nuclei: 0.194 ÷ 2 = 0.097.
The noble gas, argon, is used for
Answer: A (electric arc welding)
Argon is unreactive, so it is blown around the electric arc during welding to keep air away from the hot metal and stop it being oxidised.
A side effect of soft water is that
Answer: C (it attacks lead contained in pipes)
Soft water lacks the dissolved calcium salts that coat pipes, so it can dissolve poisonous lead from lead pipes (plumbosolvency).
Water molecules can be ligands especially when they are bonded to
Answer: C (transition metals)
Transition metal ions have empty d-orbitals that accept lone pairs from water molecules, forming complex ions such as [Cu(H2O)6]2+.
The air pollutant unknown in nature is
Answer: D (DDT)
NO, CO and methanal (HCHO) are all produced by natural processes, but DDT is a synthetic insecticide made only by man.
1.0 dm3 of distilled water was used to wash 2.0 g of a precipitate of AgCl. If the solubility product of AgCl is 2.0 × 10−10 mol2dm−6, what quantity of silver was lost in the process?
Answer: D (1.414 × 10−5 mol dm−3)
Solubility = √Ksp = √(2.0 × 10−10) = 1.414 × 10−5 mol dm−3, so that much silver dissolves in the wash water.
Hydration of ions in solution is associated with
Answer: D (liberation of heat)
When water molecules surround and attract ions, energy is given out, so hydration is exothermic (heat is liberated).
The diagram above is the solubility curve of a solute, X. Find the amount of X deposited when 500cm3 of a solution of X is cooled from 60°C to 20°C.
Answer: A (0.750 mole)
From the curve the solubility falls by about 1.5 mol dm−3 between 60°C and 20°C. In 500 cm3 (0.5 dm3), 1.5 × 0.5 = 0.75 mole is deposited.
HCl(aq) + H2O(l) ⇌ H3O+(aq) + Cl−(aq)
In the reaction above, Cl−(aq) is the
Answer: C (conjugate base)
HCl gives away a proton and becomes Cl−, so Cl− is the conjugate base of the acid HCl.
The pOH of a solution of 0.25 mol dm−3 of hydrochloric acid is
Answer: B (13.40)
pH = −log 0.25 = 0.60, so pOH = 14 − 0.60 = 13.40.
MnO4−(aq) + 8H+(aq) + Y → Mn2+(aq) + 4H2O(l)
Y in the equation above represents
Answer: C (5e−)
Manganese goes from +7 in MnO4− to +2, so it gains 5 electrons. (Charge check: −1 + 8 − 5 = +2.)
½Zn2+(aq) + e− → ½Zn(s)
In the reaction above, calculate the quantity of electricity required to discharge zinc. [F = 96 500 C mol−1]
Answer: C (9.650 × 104 C)
The equation as written uses one mole of electrons, which is 1 faraday = 96 500 C = 9.650 × 104 C.
Given that M is the mass of substance deposited in an electrolysis and Q the quantity of electricity consumed, then Faraday's law can be written as
Answer: D (M = QZ)
Faraday's first law says the mass deposited is proportional to the charge passed: M = ZQ, where Z is the electrochemical equivalent.
0.46g of ethanol when burned raised the temperature of 50 g of water by 14.3 K. Calculate the heat of combustion of ethanol.
[C = 12, O = 16, H = 1, Specific heat capacity of water = 4.2 Jg−1K−1]
Answer: C (−300 kJ mol−1)
Heat = 50 × 4.2 × 14.3 ≈ 3003 J. 0.46 g of ethanol (M = 46) is 0.01 mol, so 3003 ÷ 0.01 ≈ 300 kJ mol−1; combustion gives out heat, so ΔH = −300 kJ mol−1.
Powdered marble reacts faster with hydrochloric acid solution than the granular form because the powdered form has
Answer: C (larger surface area)
Powder exposes much more surface to the acid, so more particles collide per second and the reaction is faster.
The graph that describes a zero order reaction is
Answer: B (B)
In a zero order reaction the rate does not depend on concentration, so the graph of rate against concentration is a horizontal line (graph B).
N2(g) + O2(g) ⇌ 2NO(g); ΔH = + 180.6kJ mol−1
In the reaction above, increase in temperature will
Answer: B (increase the yield of NO)
The forward reaction is endothermic (ΔH positive), so raising the temperature shifts the equilibrium to the right and more NO is formed.
For a reaction in equilibrium, the species involved in the equilibrium constant expression are
Answer: D (gaseous and dissolved species)
Pure solids and pure liquids have constant concentrations, so only gases and dissolved species appear in the equilibrium constant expression.
A phenomenon where an element exists in different forms in the same physical state is known as
Answer: C (allotropy)
Allotropy is the existence of an element in two or more forms in the same physical state, e.g. diamond and graphite.
The substance often use for vulcanization of rubber is
Answer: C (sulphur)
Vulcanization is heating rubber with sulphur, which forms cross-links and makes the rubber harder and more elastic.
A gas that is not associated with global warming is
Answer: D (H2)
CO2 and CH4 are greenhouse gases and sulphur oxides are atmospheric pollutants; hydrogen does not trap heat in the atmosphere.
The refreshing and characteristic taste of soda water and other soft drinks is as a result of the presence in them of
Answer: A (carbon (IV) oxide)
Soft drinks are carbonated: carbon (IV) oxide is dissolved in them under pressure, giving the fizz and slightly sharp taste.
A form of carbon used for absorbing poisonous gases and purification of noble gases is
Answer: A (wood charcoal)
Wood charcoal (activated) has a huge porous surface that adsorbs gases, so it is used in gas masks and to purify gases.
Synthesis gas is a mixture of
Answer: D (CO and H2)
Synthesis gas (syngas) is a mixture of carbon (II) oxide and hydrogen, made by passing steam over hot methane or coke.
Potassium vapour burns with a
Answer: C (violet flame)
Potassium compounds and vapour give a lilac (violet) flame; sodium gives golden-yellow and calcium brick-red.
A common characteristics of copper and silver in their usage as coinage metals is that they
Answer: B (are not easily oxidized)
Coins must last a long time, and copper and silver are low in the activity series, so they do not corrode (get oxidized) easily.
Haematite is an ore of
Answer: C (iron)
Haematite is Fe2O3, the main ore of iron.
The least easily oxidized of the metals below is
Answer: C (Zn)
Of these metals zinc is lowest in the activity series, so it loses electrons least readily.
The repeating unit in natural rubber is
Answer: B (isoprene)
Natural rubber is a polymer of isoprene (2-methylbuta-1,3-diene). Neoprene is a synthetic rubber.
Unsaturated organic compounds are identified by decolourization of
Answer: B (bromine water and acidified potassium tetraoxomanganate (VII) solution)
A C=C or C≡C bond decolourises reddish-brown bromine water and purple acidified potassium tetraoxomanganate (VII) solution.
The conditions necessary for the extraction of a water molecule from two molecules of ethanol are
Answer: A (less acid and a lower temperature)
Removing one water molecule from two ethanol molecules gives ethoxyethane (ether); this needs excess ethanol (less acid) at a lower temperature (about 140°C). Excess acid at 170°C gives ethene.
The chlorinated alkane often used industrially to remove grease is
Answer: A (tetrachloromethane)
Tetrachloromethane (CCl4) is a good non-polar solvent for oils and grease and was widely used in dry cleaning.
The reaction of carbide with water gives
Answer: A (ethyne)
Calcium carbide reacts with water: CaC2 + 2H2O → Ca(OH)2 + C2H2 (ethyne).
CH3—CH2—C(=O)—OCH2CH3
The compound above is an
Answer: B (ester)
The —COO— group joining two alkyl groups is the ester linkage; this is ethyl propanoate.
Alkanones are generally obtained by the oxidation of
Answer: B (secondary alkanols)
Oxidising a secondary alkanol gives an alkanone (ketone); primary alkanols give alkanals and acids, and tertiary alkanols resist oxidation.
Sucrose is made up of
Answer: B (glucose and fructose)
Sucrose is a disaccharide; hydrolysis splits it into one glucose and one fructose unit.