All 20 questions from the Post-UTME Screening (Post-UTME) Chemistry 2017 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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120cm3 of hydrogen were sparked with 60cm3 of oxygen at 110 degrees C. What was the volume of steam produced? 2H2(g)+O2(g) -> 2H2O(g)
O2 (60cm3) is the limiting/matching reagent for 120cm3 H2 (2:1 ratio); by the 2:2 mole ratio of H2:H2O, 120cm3 H2 gives 120cm3 steam.
Catalytic hydrogenation of oils results in the production of
Hydrogenation of unsaturated vegetable oils converts them into solid/semi-solid fats used to make margarine.
Which of the following compounds will undergo addition reaction?
Ethyne (an alkyne) has a carbon-carbon triple bond and is unsaturated, so it readily undergoes addition reactions.
The products of the electrolysis of dilute sodium chloride solution with platinum electrodes are
In dilute brine, OH- is preferentially discharged over Cl- at the anode (giving oxygen) and H+ at the cathode (giving hydrogen); chlorine is only favoured in concentrated brine.
When starch undergoes complete enzyme-catalyzed hydrolysis, the resulting product is
Complete hydrolysis of starch (a glucose polymer) by amylase/other enzymes ultimately yields glucose.
Compounds that have the same molecular formula but different structure are said to be
Isomers share the same molecular formula but differ in structural arrangement.
The maximum number of electrons that can be accommodated in the shell having the principal quantum number 3 is
Maximum electrons in shell n = 2n^2 = 2(3)^2 = 18.
The following acids are non-basic except
Ethanedioic (oxalic) acid is dibasic (diprotic), able to donate two protons, unlike the other monobasic acids listed.
What is the quantity of electricity when a current of 0.5A is passed for 45mins? (F=96500C)
Q = It = 0.5 x (45x60) = 1350C. In Faradays, 1350/96500 = approx 0.014F, closest listed option is A.
Which of the following pH values would be that of a slightly alkaline system?
A pH just above 7 (neutral) indicates a slightly alkaline solution; of the choices, 8 fits.
The cleansing action of soap in hard water is not satisfactory because soap
In hard water, soap reacts with calcium and magnesium ions to form insoluble scum (salts), reducing its cleansing effectiveness.
If the solubility of KHCO3 is 0.40 mol/dm3 at room temperature, calculate the mass of KHCO3 in 100cm3 of the solution at that temperature.
Moles = 0.40 x 0.100 = 0.040mol. Molar mass KHCO3 = 100g/mol. Mass = 0.040 x 100 = 4.0g.
An acid salt can be produced using
Acid salts form from polybasic (e.g. dibasic) acids like tetraoxosulphate(VI) acid, which can be only partially neutralised.
Which of the following is deliquescent?
Sodium hydroxide (NaOH) is a classic deliquescent substance, absorbing moisture from the air until it dissolves.
One of the products formed when chlorine is bubbled slowly through a solution of potassium iodide is
Chlorine displaces iodine from potassium iodide (Cl2 + 2KI -> 2KCl + I2), producing iodine, which appears as a solid/dark precipitate.
Which of the following is produced by each of NaNO3, Pb(NO3)2 and AgNO3 when decomposed by heat?
All nitrates release oxygen gas as a common product upon thermal decomposition, alongside other products depending on the metal.
In the extraction of iron, limestone is fed into the furnace to provide
Limestone decomposes in the furnace to form calcium oxide, which reacts with silica impurities to form slag, removing them from the molten iron.
Electrolytic method is usually employed in the extraction of
Aluminium, being highly reactive, is extracted by electrolysis of its molten oxide (in cryolite).
The compound of sodium used in the manufacture of glass is
Sodium carbonate (washing soda, Na2CO3.10H2O) is used as a raw material in glass manufacture.
Which of the following is typical of transition metals?
Transition metals characteristically exhibit variable (multiple) oxidation states/valences.
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