Ethanol burns in air
5 marks · HardA student investigates the combustion of ethanol and oxidation by potassium dichromate. Study the following information and answer the questions that follow.
Write the structural formula of ethanol.
Ethanol burns completely in air. Name the two products formed in this reaction and state whether this reaction is exothermic or endothermic.
Describe what is observed when ethanol is warmed with acidified potassium dichromate(VI) solution.
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) CH3CH2OH or CH2CH3OH
(b) carbon dioxide and water; exothermic
(c) The orange solution turns green
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct structural formula: CH3CH2OH or CH2CH3OH
B2 (b) · 1 mark · Names both products: carbon dioxide and water
B3 (b) · 1 mark · Correctly identifies the reaction as exothermic
B4 (c) · 2 marks · Observation: solution turns from orange to green (1 mark for stating colour change; 1 mark for correct direction)
Worked solution
(a) The structural formula for ethanol is CH3CH2OH.
(b) When burned completely, ethanol forms carbon dioxide and water. The reaction is exothermic as it releases heat.
(c) When ethanol is warmed with acidified potassium dichromate(VI) solution, the orange solution changes to green.