All 10 questions from the Post-UTME Screening (Post-UTME) Chemistry 2010 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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How many grams of HBr would exactly be required to react with 2g of propyne? (C=12, H=1, Br=80)
Molar mass of propyne (C3H4)=40g/mol; moles=2/40=0.05mol. CH≡CCH3+HBr→CH2=CBrCH3 is 1:1, so 0.05mol HBr needed. Molar mass HBr=81; mass=0.05×81≈4.1g.
If an organic compound decolorizes bromine water, then the compound is
Decolorizing bromine water is a classic test for unsaturation (C=C double bonds).
A mixture contains 20cm³ of hydrogen, 35cm³ of oxygen, 15cm³ of carbon dioxide and 10cm³ of nitrogen at S.T.P, which of the following gives the mole fraction of hydrogen in this mixture?
Total volume=20+35+15+10=80cm³; mole fraction of H2=20/80=0.25.
Which of the following is a neutralization reaction? Addition of
Neutralization is the reaction of an acid with a base — nitric acid with sodium hydroxide.
The pH of four solutions W, X, Y, Z are 4, 6, 8, 10 respectively, therefore
The lowest pH (4) indicates the most acidic solution, which is W.
When ammonium, potassium and calcium carbonates are each separately heated
Ammonium carbonate decomposes on heating into carbon dioxide, water and ammonia (unlike the more thermally stable potassium carbonate).
Equilibrium is said to be attained in a reversible reaction when
Chemical equilibrium is defined by equal forward and backward reaction rates.
The metal extracted from cassiterite is
Cassiterite is the principal ore of tin (SnO2).
In the electrolysis of brine, the anode is
In brine electrolysis, an inert carbon (graphite) electrode is typically used as the anode.
Vulcanization involves the removal of
Vulcanization cross-links rubber polymer chains via sulfur, consuming some of the double bonds present in the rubber.
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