Alkenes
7 marks · HardThis question is about drawing and naming alkenes and their reactions.
Draw the displayed formula of propene (C3H6). Name the type of bond responsible for its unsaturation.
State the product and write the balanced chemical equation for the reaction between propene and hydrogen gas.
Name the organic product and give its molecular formula when propene reacts with steam in the presence of a catalyst.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Displayed formula for propene (CH2=CH–CH3 or full displayed structure); The bond responsible is the carbon–carbon double bond (C=C).
(b) Product: propane; Balanced equation:
(c) Product: propan-2-ol (the major product expected for hydration of propene at this level); Molecular formula:
Common mistakes: Naming bond as 'hydrogen bond'; Incorrect product name/formula
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct displayed formula for propene (all atoms and bonds shown).
B2 (a) · 1 mark · Names C=C as the bond responsible for unsaturation.
M1 (b) · 1 mark · Identifies product as propane.
A1 (b) · 1 mark · Correct balanced equation: .
M2 (c) · 1 mark · Product named correctly as propan-2-ol.
A2 (c) · 1 mark · Correct molecular formula: .
A3 (c) · 1 mark · Name and formula clearly linked to hydration reaction.
Worked solution
a) Displayed formula for propene: (students should draw) H2C=CH–CH3. The bond responsible for unsaturation is the carbon–carbon double bond (C=C).
b) Propene reacts with hydrogen to form propane:
c) Propene + steam → propan-2-ol (major product). Molecular formula: .