17 questions. Try each one, then open the answer to check yourself and read the explanation.
Sodium chloride can be obtained from brine through
Answer: C (evaporation)
Brine is salt dissolved in water; evaporating the water leaves the solid sodium chloride behind.
NH4NO2(s) → (heat) N2(g) + 2H2O(l)
In the above reaction, calculate the volume of N2(g) that would be produced at S.T.P from 3.20g of NH4NO2(s) [N=14, H=1, O = 16] Molar volume at s.t.p. = 22.4dm3
Answer: C (1.12dm3)
Molar mass of NH4NO2 = 64 g, so 3.20 g = 0.05 mol, giving 0.05 mol of N2. Volume = 0.05 × 22.4 = 1.12 dm3.
In the above electrolyte cell, which species migrate to the anode?
Answer: B (SO42− and OH−)
The anode is positive, so the negative ions in K2SO4(aq), SO42− and OH−, move to it.
What is the approximate volume of air containing 10cm3 of oxygen?
Answer: D (50cm3)
Air is about one-fifth (20%) oxygen, so 10 cm3 of oxygen is in about 5 × 10 = 50 cm3 of air.
The above diagram illustrates the energy profile of the catalyst and uncatalysed reaction of A(g) + B(g) → AB(g). Calculate the activation energies in KJ of the catalysed and uncatalysed unreverse reactions.
Answer: B (300, 500)
Activation energy = peak energy − reactant energy. Catalysed: 400 − 100 = 300 kJ; uncatalysed: 600 − 100 = 500 kJ.
A property found in a colloidal dispersion which is absent in a true solution is
Answer: B (the Tyndale effect)
Colloid particles are big enough to scatter a beam of light (the Tyndall effect); a true solution does not.
A gas when dissolved in water vapour, produced acid rain during rainfall. The gas is
Answer: C (sulphur (IV) oxide)
SO2 dissolves in rainwater to form trioxosulphate(IV) acid, a major cause of acid rain.
The carbon atoms in H2C=CH2 are
Answer: D (Sp2 hybridized)
Each carbon in ethene forms three σ bonds and one π bond, so it uses sp2 hybrid orbitals.
Half cell reaction — Eθ
Cu2+(aq) + 2e− → Cu(s) +0.34V
Zn2+(aq) + 2e− → Zn(s) −0.76V
Fe2+(aq) + 2e− → Fe(s) −0.44V
Ba2+(aq) + 2e− → Ba(s) −2.90V
From the above data, it can be deduced that the most powerful reducing agent is?
Answer: D (Ba)
The most negative electrode potential (−2.90 V for Ba) means the metal loses electrons most easily, so barium is the strongest reducing agent.
CH3CH2OH + CH3COOH → (Conc H2SO4) Y + Z
Y and Z in the reaction above represent
Answer: D (CH3COOCH2CH3 and H2O)
An alkanol and an alkanoic acid react (esterification) to give an ester, ethyl ethanoate, and water.
Write out the increasing oxidation number of the transition metal ion for the compounds K2Cr2O7, V2O5 and KMnO4.
Answer: B (V2O5 < K2Cr2O7 < KMnO4)
V in V2O5 is +5, Cr in K2Cr2O7 is +6 and Mn in KMnO4 is +7.
Given the distance between the nuclei of chlorine atoms in a chlorine molecule as 0.194mm, calculate its atomic radius.
Answer: B (0.097mm)
The nucleus-to-nucleus distance is two atomic radii, so r = 0.194/2 = 0.097.
Which of these equations shows that a reaction is in equilibrium?
Answer: C (ΔG = O)
At equilibrium there is no driving force in either direction, so the free energy change ΔG is zero.
The formula CH2O for ethanoic acid represents its
Answer: D (empirical formula)
Ethanoic acid is C2H4O2 = (CH2O)2; CH2O is the simplest whole-number ratio, the empirical formula.
How is Cl2(g) prepared in the laboratory? by
Answer: D (dropping concentrated hydrochloric acid unto potassium tetraoxomanganate(VI) crystals)
Concentrated HCl is oxidised to chlorine by potassium permanganate crystals without heating (option A gives HCl gas, not chlorine).
Which of the following is an isomer of C5H12?
Answer: A (2-methylbutane)
2-methylbutane has five carbons and twelve hydrogens, the same formula as pentane but a branched chain.
According to Charles's law, at what temperature does the volume of gas becomes zero?
Answer: D (−273°C)
Extending the volume-temperature line to zero volume gives absolute zero, −273 °C (0 K).