Chemistry WCH14 May 2020 Questions & Answers

Questions And Worked Solutions For Chemistry WCH14 May 2020

IAL Chemistry WCH14 May 2020 Questions - Complete Paper (pdf)

1. Bromine oxidises methanoic acid to carbon dioxide.
2. The rate of the reaction between two compounds, Y and Z, was investigated.
   The results are shown.
3. The inorganic anti-cancer drug cis-platin, Pt(NH₃)₂Cl₂, is hydrolysed by water to make it active. The reaction is
4. Propanone reacts with iodine in acidic solution.
5. The equation shows the hydrolysis of a bromoalkane
6. The equation for an exothermic reaction is shown.
7. The equation for the equilibrium decomposition of hydrogen iodide into hydrogen and iodine can be written in two ways.
8. A buffer solution contains ethanoic acid, with a concentration of 0.10 mol dm⁻³, and sodium ethanoate, with a concentration of 0.050 mol dm⁻³.
9. The graphs show the changes in pH during a series of titrations.
   Each titration involves two solutions, each of concentration 0.1moldm⁻³.
10. Which diagram shows the first step of the mechanism for the nucleophilic addition of hydrogen cyanide to propanone in the presence of potassium cyanide?
11. When propanone reacts with iodine in the presence of sodium hydroxide, the precipitate formed has the formula
12. Which of the following could not be formed when methylamine is added to ethanoyl chloride?
13. In which of these esters is the percentage by mass of carbon 54.5%?
14. An organic compound that reacts with both lithium tetrahydridoaluminate(III) (lithium aluminium hydride) and magnesium could be
15. The following methods can be used to distinguish between pairs of organic compounds with no further tests.

16. This question concerns calcium chloride, CaCl₂.
    (a) Some energy changes related to calcium chloride are shown
17. This question concerns six isomers each with the molecular formula C₅H₁₀O₂.
    (a) Isomers A, B, C and D are structural isomers that all react with aqueous sodium carbonate to produce carbon dioxide.
    Isomer A is a straight-chain compound.
    Isomer B has only two peaks in its high resolution proton NMR spectrum, both of which are singlets.
    Isomer C contains a chiral centre but isomer D does not.
    Give the structures of these four isomers.
18. This question concerns acidic solutions.
    (a) (i) A solution of hydrochloric acid has a pH of 1.125.
    Calculate the concentration of hydrogen ions and of hydroxide ions, in mol dm⁻³, in this solution
    (ii) Calculate the volume of water which must be added to 25.0 cm³ of this solution to increase the pH from 1.125 to 1.500, giving your answer to an appropriate number of significant figures.
    (b) Phosphoric(V) acid, H₃PO₄ , is a weak acid, which dissolves in water, giving the equilibrium
    (i) Identify the acids and bases in the spaces below Equation 2, linking the acid-base conjugate pairs.
    (ii) Explain why very little dissociation of the H₃PO₄⁻ ion occurs in solutions of phosphoric(V) acid.

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