Addition reactions of alkenesEdexcel International A Level Chemistry: Subtopic test

1. 1
   Margarine manufacturers harden liquid vegetable oils, whose molecules contain C=C bonds, by reacting them with hydrogen gas in the presence of a nickel catalyst. Relative atomic masses are given where needed, and the molar volume of a gas at room temperature and pressure is 24.0 dm³ mol⁻¹.

   (a)

   Propene reacts with hydrogen gas over a nickel catalyst. What is the product, and what type of reaction is this?

   [1 mark]

   • APropane; addition
   • BPropan-2-ol; addition
   • CPropane; substitution
   • DPropyne; elimination

   (b)

   0.25 mol of hexa-1,5-diene, C₆H₁₀, is fully hydrogenated over a nickel catalyst. What volume of hydrogen is needed?

   [1 mark]

   • A6.0 dm³
   • B24.0 dm³
   • C12.0 dm³
   • D48.0 dm³

   (c)

   A student shakes a sample of the vegetable oil with bromine water. State the colour change and explain what it shows.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Ethanol for industrial use is made from ethene, which comes from the cracking of oil. Ethene also undergoes several other addition reactions that a chemist is investigating.

   (a)

   Which reagent converts ethene into ethanol in a single addition step?

   [1 mark]

   • AHydrogen with a nickel catalyst
   • BSteam with an acid catalyst
   • CBromine water
   • DAcidified potassium manganate(VII)

   (b)

   What is the organic product when ethene reacts with bromine?

   [1 mark]

   • A1,1-Dibromoethane
   • BBromoethane
   • C1,2-Dibromoethene
   • D1,2-Dibromoethane

   (c)

   Write the equation for the reaction of ethene with steam to make ethanol, and name a suitable catalyst.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A technician has two unlabelled colourless liquids, one hexane and one hex-1-ene. Separately, she studies the oxidation of propene by cold, dilute, acidified potassium manganate(VII).

   (a)

   Describe a test that would identify which liquid is hex-1-ene, stating the observation for each liquid.

   [3 marks]

   (b)

   Propene is bubbled through cold, dilute, acidified potassium manganate(VII). State the observation, name the organic product, write an equation using [O] to represent the oxidising agent, and state the role of manganate(VII).

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A chemist is planning reactions of alkenes obtained from cracking. Relative atomic masses: H = 1.0, C = 12.0, Br = 80.0.

   (a)

   Show how but-2-ene can be converted by three different addition reactions into three different products, giving for each the reagent(s), conditions and the name of the organic product.

   [6 marks]

   (b)

   A 2.80 g sample of an alkene Q, CₙH₂ₙ, reacts with exactly 8.00 g of bromine in an addition reaction. Calculate the molar mass of Q, deduce its molecular formula and calculate the mass of the dibromoalkane formed, assuming a 100% yield.

   [6 marks]

   Total for question 4: 12 marks

End of questions