44 questions. Try each one, then open the answer to check yourself and read the explanation.
The presence of an impurity in substance will cause the melting point to
Answer: B (reduce.)
Impurities disturb the regular arrangement of particles, so a solid melts at a lower temperature (and over a range).
What volume of carbon(II) oxide is produced by reacting excess carbon with 10 dm3 of oxygen?
Answer: B (20 dm3)
2C + O2 → 2CO: 1 volume of oxygen gives 2 volumes of CO, so 10 dm3 gives 20 dm3.
From the diagram above, an ideal gas is represented by
Answer: A (Z)
For an ideal gas PV stays constant as P changes, so the graph is the horizontal line Z.
The radioisotope used in industrial radiography for the rapid checking of faults in welds and casting is
Answer: C (cobalt-60.)
Cobalt-60 gives penetrating gamma rays that pass through metal and show hidden cracks.
How many unpaired electrons are in the p-orbitals of a fluorine atom?
Answer: C (1)
Fluorine is 1s22s22p5: 2px2 2py2 2pz1, so one electron is unpaired.
The radioactive emission with the least ionization power is
Answer: C (γ-rays.)
Gamma rays have no charge and no mass, so they ionise least (but penetrate most); alpha particles ionise most.
The shape of the carbon(IV) oxide molecule is
Answer: B (linear.)
O=C=O: the two double bonds point in opposite directions, at 180°, so the molecule is linear.
Which of the following molecules is held together by hydrogen bond?
Answer: D (HF)
Hydrogen bonds form when H is bonded to a very electronegative small atom (F, O or N); HF molecules are linked this way.
The bond formed between two elements with electron configurations 1s2 2s2 2p6 3s2 and 1s2 2s2 2p4 is
Answer: D (ionic.)
The first is magnesium (gives 2 electrons) and the second oxygen (takes 2), so they form ionic MgO.
The constituent of air that acts as a diluent is
Answer: A (nitrogen.)
Nitrogen (about 78% of air) is unreactive and dilutes the oxygen, slowing down burning and respiration.
An example of a hygroscopic substance is
Answer: A (CuO(s))
Copper(II) oxide absorbs moisture from the air without dissolving in it (hygroscopic); MgCl2, CaCl2 and NaOH absorb enough to dissolve (deliquescent).
If 24.4 g of lead(II) trioxonitrate(V) were dissolved in 42 g of distilled water at 20°C, calculate the solubility of the solute in gdm−3.
Answer: A (581.000)
42 g of water is about 42 cm3. Per 1000 cm3: 24.4 × 1000/42 = 581 g dm−3.
In a water body, too much sewage leads to
Answer: C (an increase in the bacterial population which reduces the level of oxygen in the water.)
Bacteria multiply as they feed on the sewage and use up the dissolved oxygen, which suffocates fish.
10.0 dm3 of water was added to 2.0 mol dm−3 of 2.5dm3 solution of HCl. What is the concentration of the final solution in mol dm−3?
Answer: A (0.4)
C1V1 = C2V2: 2.0 × 2.5 = C2 × 12.5, so C2 = 0.4 mol dm−3.
Three drops of a 1.0 mol dm−3 solution of HCl was added to 20 cm3 of a solution of pH6.4. The pH of the resulting solution will be
Answer: B (less than 6.4.)
Adding a strong acid increases the H+ concentration, so the pH falls below 6.4.
Which of the following substances is not a salt?
Answer: A (Aluminium oxide)
Aluminium oxide is an (amphoteric) oxide; the others are salts made from an acid and a base.
An insoluble salt can be prepared by
Answer: B (double decomposition.)
Mixing solutions of two soluble salts precipitates the insoluble salt (double decomposition), which is filtered off.
2H2O(l) + 2F2(g) → 4HF(aq) + O2(g)
In the reaction above, the substance that is being reduced is
Answer: C (F2(g))
Fluorine goes from 0 in F2 to −1 in HF: it gains electrons, so it is reduced.
Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s)
In the reaction above, the oxidizing agent is
Answer: A (CuSO4(aq))
Cu2+ in CuSO4 takes electrons from zinc and is reduced to Cu, so CuSO4 is the oxidizing agent.
In an electrochemical cell, polarization is caused by
Answer: D (hydrogen.)
Bubbles of hydrogen collect on the positive electrode of a simple cell and reduce its voltage; this is polarization.
Calculate the volume in cm3 of oxygen evolved as s.t.p. when a current of 5 A is passed through acidified water for 193 s [F = 96500 Cmol−1, Molar volume of a gas at s.t.p. = 22.4 dm3]
Answer: D (56.000)
Q = 5 × 193 = 965 C = 0.01 F. Each mole of O2 needs 4 F, so 0.0025 mol × 22 400 cm3 = 56 cm3.
In an endothermic reaction, if there is a loss in entropy the reaction will
Answer: C (not be spontaneous.)
ΔG = ΔH − TΔS. With ΔH positive and ΔS negative, ΔG is always positive, so the reaction cannot be spontaneous.
2SO2(g) + O2(g) ⇌ 2SO3(g) ΔH = −395.7kJmol−1
In the reaction above, the concentration of SO3(g) can be increased by
Answer: B (decreasing the temperature.)
The forward reaction is exothermic, so lowering the temperature shifts the equilibrium to the right, giving more SO3.
The minimum amount of energy required for a reaction to take place is
Answer: C (activation energy.)
Activation energy is the minimum energy colliding particles need to react.
In the graph above, the activation energy of the catalyzed reaction is
Answer: A (100KJ.)
The reactants start at 100 kJ and the catalysed (lower, dashed) curve peaks at 200 kJ, so Ea = 200 − 100 = 100 kJ.
3Fe(s) + 4H2O(g) ⇌ Fe3O4(s) + 4H2(g)
The equilibrium constant, K, of the reaction above is represented as
Answer: C ([H2]4/[H2O]4)
Solids are left out of K, and products go on top raised to their coefficients: K = [H2]4/[H2O]4.
Which of the following compounds is a neutral oxide?
Answer: D (Carbon (II) oxide.)
CO reacts with neither acids nor alkalis, so it is neutral; the other three are acidic oxides.
In the laboratory preparation of ammonia, the flask is placed in a slanting position so as to
Answer: A (prevent condensed water from breaking the reaction flask.)
Water formed in the reaction condenses near the mouth; tilting the flask stops it running back onto the hot glass and cracking it.
Which of the following gases is employed as an anaesthesia?
Answer: A (N2O)
Dinitrogen(I) oxide (laughing gas) is used as a mild anaesthetic.
Sulphur(IV) oxide is a strong reducing agent in the presence of water due to the formation of
Answer: D (trioxosulphate(IV) ion.)
In water SO2 forms trioxosulphate(IV) ions, which are easily oxidised to tetraoxosulphate(VI), giving away electrons.
A metal that forms soluble trioxosulphate (IV) salt is
Answer: B (potassium.)
All potassium (group 1) salts are soluble; barium trioxosulphate(IV) is insoluble.
Copper is displaced from the solution of its salts by most metals because it
Answer: A (is at the bottom of the activity series.)
Copper is low in the activity series, so most metals above it can push it out of its salt solutions.
The coloured nature of transition metal ions are associated with their partially filled
Answer: D (d-orbital.)
Electrons moving between partly filled d-orbitals absorb visible light, so the ions appear coloured.
Aluminium containers are frequently used to transport trioxonitrate(V) acid because aluminium
Answer: B (does not react with the acid.)
Concentrated HNO3 forms a thin protective oxide layer on aluminium (it becomes passive), so the metal is not attacked.
2-methylbutan-2-ol is an example of a
Answer: D (tertiary alkanol.)
The carbon carrying the −OH is joined to three other carbon atoms, so it is a tertiary alkanol.
The reaction between ammonia and ethyl ethanoate produces
Answer: D (ethanol and ethanamide.)
CH3COOC2H5 + NH3 → CH3CONH2 (ethanamide) + C2H5OH (ethanol).
The decarboxylation of ethanoic acid will produce carbon(IV) oxide and
Answer: A (methane.)
Removing CO2 from CH3COOH leaves CH4 (methane).
The compound above is an
Answer: A (alkanone.)
The C=O group is on the middle carbon, between two carbons: CH3COCH3 (propanone), an alkanone.
The compound that will react with sodium hydroxide to form salt and water only is
Answer: D (CH3CH2COOH.)
Propanoic acid is an acid, so it neutralises NaOH to give sodium propanoate and water.
Which of the following compounds in solution will turn red litmus paper blue?
Answer: C (RNH2)
Amines, like ammonia, have a lone pair on nitrogen that accepts protons, so their solutions are alkaline.
The dehydration of ammonium salt of alkanoic acids produces a compound with the general formula.
Answer: B (RCONH2)
RCOONH4 → RCONH2 + H2O: heating the ammonium salt removes water and gives an amide.
An organic compound with a pleasant smell is likely to have a general formula
Answer: C (CnH2n+1COOCnH2n+1.)
Esters (RCOOR′) have pleasant, fruity smells.
A primary amide is generally represented by the formula
Answer: B (RCONH2.)
A primary amide has an unsubstituted −NH2 group: RCONH2.
An organic compound contains 60% carbon, 13.3% hydrogen and 26.7% oxygen. Calculate the empirical formula. [C = 12, H = 1, O = 16]
Answer: B (C3H8O.)
C : H : O = 60/12 : 13.3/1 : 26.7/16 = 5 : 13.3 : 1.67 = 3 : 8 : 1, so C3H8O.