All 10 questions from the Post-UTME Screening (Post-UTME) Chemistry 2011 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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One mole of propane is mixed with five moles of oxygen. The mixture is ignited, what is the volume of the products at s.t.p?
C3H8+5O2→3CO2+4H2O. 1 mole propane gives 3 moles CO2; volume=3×22.4=67.2dm³.
Which of the following acts both as a reducing and an oxidizing agent?
SO2 can act as either a reducing or oxidizing agent depending on the reaction partner.
What is the partial pressure of hydrogen gas collected over water at a standard atmospheric pressure and 25°C, if the saturation vapour pressure of water is 23mm Hg at that temperature?
Partial pressure of H2 = total pressure - vapour pressure of water = 760-23=737mmHg.
A hydrated salt of formula MSO4·xH2O contains 45.3% by mass of water of crystallization. Calculate the value of x. [M=56, S=32, O=16, H=1]
Molar mass of hydrate=152+18x. Setting 18x/(152+18x)=0.453 and solving gives x≈7.
The pOH of a solution of 0.25 mol dm⁻³ of hydrochloric acid is
pH=-log(0.25)≈0.602; pOH=14-0.602≈13.40.
½Zn²⁺(aq)+e→½Zn(s). In the reaction above, calculate the quantity of electricity required to discharge 0.5 mol of zinc. [F=96,500 C mol⁻¹]
Quantity of electricity=0.5×96500×2=9.650×10⁴C.
Deliquescent substances are used for
Deliquescent substances absorb moisture from the air and are used as drying agents (desiccants).
Which of the following best explains the increase in the rate of a chemical reaction as the temperature rises?
Per the source key, increased collision frequency is marked as the answer; note most textbooks primarily attribute the rate increase to a greater proportion of molecules exceeding the activation energy, so this is worth double-checking against your syllabus.
NH2-CH-C(=O)-OH: the two functional groups in the above compound are
This is an amino acid structure, containing both a carboxylic acid group and an amine group.
CH3C(=O)OCH2CH3 (an ester) and CH3CH2CH2C(=O)OH (a carboxylic acid) are
Both compounds share the molecular formula C4H8O2, making them (functional group) isomers.
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