45 questions. Try each one, then open the answer to check yourself and read the explanation.
What is the concentration of a solution containing 2g of NaOH in 100cm3 of solution? {Na = 23, O = 16, H = 1}
Answer: B (0.50 mol dm−3)
NaOH = 40 g/mol, so 2 g = 0.05 mol. In 0.1 dm3: 0.05/0.1 = 0.50 mol dm−3.
Which of the following properties is NOT peculiar to matter?
Answer: D (Random motion of particles increases from gas to solid.)
Particles move most randomly in a gas and least in a solid, so random motion decreases (not increases) from gas to solid.
The principle of column chromatography is based on the ability of the constituents to
Answer: A (move at different speeds in the column)
Each component is held by the column material to a different extent, so they travel at different speeds and separate.
From the diagram above, an ideal gas can be represented by
Answer: B (N)
For an ideal gas at constant temperature PV is constant (Boyle's law), so a graph of PV against P is a horizontal line, N.
An isotope has an atomic number of 15 and a mass number of 31. The number of protons it contains is
Answer: B (15)
The atomic number is the number of protons: 15.
The molecular lattice of iodine is held together by
Answer: D (van der Waal's forces)
Each I2 molecule is covalent inside, but the molecules are held to each other only by weak van der Waals forces.
The arrangement of particles in crystal lattices can be studied using
Answer: A (x-rays)
X-ray diffraction reveals how the particles are arranged in a crystal.
From the diagram above, find the amount of solute deposited when 200cm3 of the solution is cooled from 55°C to 40°C.
Answer: B (0.20 mole)
From the graph the solubility falls by about 1 mole per dm3 between 55 °C and 40 °C. For 200 cm3 (0.2 dm3): 1 × 0.2 = 0.20 mole is deposited.
The importance of sodium aluminate (III) in the treatment of water is to
Answer: A (cause coagulation)
Sodium aluminate forms a sticky aluminium hydroxide floc that clumps fine particles together (coagulation) so they settle out.
What type of bond exists between an element X with atomic number 12 and Y with atomic number 17?
Answer: A (Electrovalent.)
X is magnesium (a metal, gives 2 electrons) and Y is chlorine (a non-metal, gains 1), so they form an ionic (electrovalent) bond in MgCl2.
Hardness of water is mainly due to the presence of
Answer: B (calcium trioxocarbonate (IV) or calcium tetraoxosulphate (VI))
Hard water contains dissolved calcium (and magnesium) salts, chiefly the hydrogen trioxocarbonate(IV) and the tetraoxosulphate(VI).
Which of the following noble gases is commonly found in the atmosphere?
Answer: D (Argon.)
Argon makes up almost 1% of air, far more than any other noble gas.
N2O4(g) ⇌ 2NO2(g) ΔH = +ve
In the reaction above, an increase in temperature will
Answer: A (increase the value of the equilibrium constant)
The forward reaction is endothermic, so heating favours it and K increases.
CH3COOH(aq) + OH−(aq) ⇌ CH3COO−(aq) + H2O(l)
In the reaction above, CH3COO−(aq) is the
Answer: A (conjugate base)
CH3COOH loses a proton to become CH3COO−, so CH3COO− is its conjugate base.
How many cations will be produced from a solution of potassium aluminium tetraoxosulphate (VI)?
Answer: D (2)
KAl(SO4)2 (a double salt) gives two kinds of cation in solution: K+ and Al3+.
Which of the following is NOT an alkali?
Answer: B (Mg(OH)2)
An alkali is a base that dissolves in water. Magnesium hydroxide is practically insoluble, so it is a base but not an alkali.
An effect of thermal pollution on water bodies is that the
Answer: D (level of oxygen reduces)
Gases are less soluble in warm water, so heating a river or lake lowers its dissolved oxygen.
Which of the following is a deliquescent compound?
Answer: B (CaCl2)
Anhydrous calcium chloride absorbs so much water from the air that it dissolves in it, which is deliquescence.
A chemical reaction in which the hydration energy is greater than the lattice energy is referred to as
Answer: C (an exothermic reaction)
If more energy is released when the ions are hydrated than is needed to break the lattice, there is a net release of heat: exothermic.
The function of zinc electrode in a galvanic cell is that it
Answer: C (produces electons)
Zinc is the anode: it is oxidised (Zn → Zn2+ + 2e−), releasing electrons into the circuit.
CH4(g) + Cl2(g) → CH3Cl(s) + HCl(g)
The major factor that influences the rate of the reaction above is
Answer: D (light)
Chlorination of methane is a photochemical reaction: it needs light to split Cl2 into free radicals.
The condition required for corrosion to take place is the presence of
Answer: D (water and oxygen)
Iron rusts only when both water and oxygen are present.
In the diagram above, X is the
Answer: B (enthalpy change)
X is the energy gap between reactants and products, which is the enthalpy change (ΔH) of the reaction.
The diagram above best illustrates the effect of decrease in
Answer: A (concentration)
As the reaction goes on, reactants are used up and their concentration falls, so the rate drops with time as shown.
MnO4−(aq) + Y + 5Fe2+(aq) → Mn2+(aq) + 5Fe3+(aq) + 4H2O(l)
In the equation above, Y is
Answer: D (8H+(aq))
The 4 O atoms of MnO4− form 4H2O, which needs 8 H atoms, so Y = 8H+. Charges check: −1 + 8 + 10 = +17 = +2 + 15.
Given that M is the mass of a substance deposited during electrolysis and Q is the quantity of electricity consumed, then Faraday's first law can be written as [E = Electrochemical equivalent]
Answer: B (M = EQ)
Faraday's first law: mass deposited is proportional to charge passed, M = EQ, where E is the electrochemical equivalent.
The impurities formed during the laboratory preparation of chlorine gas are removed by
Answer: A (H2O)
The main impurity is hydrogen chloride gas, which is removed by bubbling the chlorine through water (conc. H2SO4 then only dries it).
The effect of the presence of impurities such as carbon and sulphur on iron is that they
Answer: D (lower its melting point)
Impurities lower the melting point of iron (cast iron melts lower than pure iron) and make it brittle.
A few drops of concentrated HNO3 is added to an unknown solution and boiled for a while. If this produces a brown solution, the cation present is likely to be
Answer: D (Fe2+)
Concentrated HNO3 oxidises pale-green Fe2+ to Fe3+, giving a yellow-brown solution.
The bleaching action of chlorine gas is effective due to the presence of
Answer: B (water)
Chlorine bleaches only when moist: with water it forms HOCl, which releases oxygen that oxidises the dye.
In the laboratory preparation of oxygen, dried oxygen is usually collected over
Answer: B (mercury)
Collecting over water would make the gas wet again, so dry oxygen is collected over mercury (it is dried with conc. H2SO4 first).
The property of concentrated H2SO4 that makes it suitable for preparing HNO3 is its
Answer: A (boiling point)
Concentrated H2SO4 has a high boiling point (it is non-volatile), so it displaces the more volatile HNO3 from a nitrate, which distils off.
Bronze is preferred to copper in the making of medals because it
Answer: A (is stronger)
Alloying copper with tin makes bronze harder and stronger, and more resistant to corrosion, so medals keep their shape and look.
The constituent of baking powder that makes the dough to rise is
Answer: A (NaHCO3)
Sodium hydrogen trioxocarbonate(IV) releases CO2 when heated or with acid, and the gas bubbles make the dough rise.
Which of the following compounds is used as a gaseous fuel?
Answer: D (CH3 − CH2 − CH2 − CH3)
Butane is the gas in cooking-gas cylinders (LPG).
The ability of carbon to form long chains is referred to as
Answer: C (catenation)
Catenation is the joining of atoms of the same element into chains or rings.
Which of the following compounds will undergo polymerization reaction?
Answer: A (C2H4)
Ethene has a C=C double bond, so many molecules can add together to form poly(ethene).
The compound above exhibits
Answer: B (optical isomerism)
The central carbon carries four different groups (H, OH, CH3, COOH), so it is chiral and shows optical isomerism.
An organic compound has an empirical formula CH2O and vapour density of 45. What is its molecular formula? [C = 12, H = 1, O = 16]
Answer: C (C3H6O3)
Molar mass = 2 × 45 = 90. CH2O = 30, so n = 3 and the formula is C3H6O3.
C6H12O6 → 2C2H5OH + 2CO2 + Energy (zymase, 250C)
The reaction represented by the equation above is useful in the production of
Answer: D (ethanol)
This is fermentation of glucose by yeast (zymase), which produces ethanol.
The number of isomers that can be obtained from C4H10 is
Answer: D (2)
C4H10 exists as butane and 2-methylpropane: 2 isomers.
Which of the following is a primary amine?
Answer: B (CH3NH2)
A primary amine has one alkyl group on the nitrogen (R−NH2). CH3CONH2 is an amide, not an amine.
Two organic compounds K and L were treated with a few drops of Fehling's solution respectively. K formed a brick-red precipitate while L remains unaffected. The compound K is an
Answer: C (alkanal)
Alkanals (aldehydes) reduce Fehling's solution to red Cu2O; alkanones do not.
Which of the following statements is true about 2-methylpropane and butane?
Answer: A (They are members of the same homologous series.)
Both are C4H10 alkanes, so they belong to the alkane series; being isomers, they have different boiling points.
CH3COOH + C2H5OH → CH3COOC2H5 + H2O (conc. H2SO4)
The reaction above is best described as
Answer: A (esterification)
An alkanoic acid reacting with an alkanol to give an ester and water is esterification.