Chemistry WCH14 January 2021 Questions & Answers

Questions And Worked Solutions For Chemistry WCH14 January 2021

IAL Chemistry WCH14 January 2021 Questions - Complete Paper (pdf)

1. Which of these has the highest standard molar entropy at 298 K and 1 atm pressure?
2. The entropy change of the surroundings
3. Which equation represents the standard enthalpy change of atomisation
4. This question is about four ionic compounds
5. The standard enthalpy change of solution of potassium chloride, KCl, is +17 kJ mol⁻¹.
6. The total entropy change
7. Propanone reacts with iodine in the presence of a catalyst of dilute hydrochloric acid. The reaction occurs in aqueous solution.
8. The rate equation for a reaction is
9. This question is about weak acids.
10. A titration was carried out by adding 0.1 mol dm⁻³ hydrochloric acid to 0.1 mol dm⁻³ aqueous ammonia.
11. A diprotic acid, H₂A, was titrated with sodium hydroxide solution.
12. A sample of a bromoalkane, RBr, containing a single optical isomer reacts with hydroxide ions in an S_N1 mechanism.
13. A compound X, with molecular formula C₅H₁₀O , gave an orange precipitate with 2,4-dinitrophenylhydrazine
14. Propyl ethanoate, CH₃COOCH₂CH₂CH₃ , is hydrolysed with aqueous sodium hydroxide. Which products are formed?
15. 2.95 g of ethanoic acid is produced from 2.50 g of ethanol. What is the percentage yield of ethanoic acid?
16. A mixture of organic compounds was analysed using thin-layer chromatography

17. This question is about carboxylic acids and their derivatives.
18. This question is about sulfuric acid and its salts.
    (a) The manufacture of sulfuric acid involves the equilibrium
    (i) A catalyst of vanadium(V) oxide is used in this reaction.
    State the effect, if any, of the catalyst on the value of the equilibrium constant, Kp.
    (ii) The temperature used for this reaction in industry is 700 K.
    Explain, in terms of the equilibrium constant and the equilibrium position, the effect of an increase in temperature on the equilibrium yield of sulfur trioxide.
    (iii) Write the expression for the equilibrium constant, Kp , for this equilibrium.
    State symbols are not required.
    (iv) A mixture of 2.00 mol of sulfur dioxide and 1.00 mol of oxygen is allowed to reach equilibrium at 5.00 atm pressure.
    1.60 mol of sulfur trioxide is formed.
    Calculate the value of Kp .
    Include units and give your answer to an appropriate number of significant figures.
    (b) Sulfur trioxide is used to produce sulfuric acid.
    (i) Commercial concentrated sulfuric acid contains 98.5 % H₂SO₄ and 1.5 % water by mass.
    The density of concentrated sulfuric acid is 1800 g dm⁻³.
    Calculate the concentration of this sulfuric acid in mol dm⁻³.
    (ii) The pH of a 0.10 mol dm⁻³ solution of sulfuric acid at 25 °C is 0.97.
    Calculate the concentration of hydrogen ions, in mol dm⁻³, in this solution
    (iii) In an aqueous solution of sulfuric acid, the following equilibria exist.
    (c) A buffer solution is made from HSO₄⁻ and SO₄^2- ions
    
19. This question is about carbonyl compounds.
    (a) The skeletal formula of menthone is shown.

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