Carboxylic Acids
6 marks · NormalA student is learning about carboxylic acids and how they react with metals.
State the name of the unbranched-chain carboxylic acid with two carbon atoms.
Write the molecular formula for the acid you named in (a).
When this acid reacts with zinc metal, a salt and hydrogen gas are produced.
i. Write a balanced chemical equation (using molecular formulae) for the reaction between the acid from (a) and zinc metal.
Name the salt formed in the reaction in part (c).
Give one observation you would expect when this reaction takes place.
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.
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(a) ethanoic acid
(b) C2H4O2
(c) Zn + 2CH3COOH → (CH3COO)2Zn + H2
(d) zinc ethanoate
(e) Fizzing or effervescence (release of a gas)
Common mistakes: Wrong acid name (e.g., 'methanoic acid'); Incorrect formula (e.g., omission of O atoms); Incorrectly balanced equation; Wrong salt name (e.g., 'ethanoic zinc')
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Marking points
B1 (a) · 1 mark · Correct name of the two-carbon unbranched carboxylic acid (ethanoic acid)
B2 (b) · 1 mark · Correct molecular formula given (C2H4O2)
M1 (c) · 1 mark · Correct reactants and products in a balanced equation (Zn + 2CH3COOH → (CH3COO)2Zn + H2)
A1 (c) · 1 mark · Correct balancing in the equation
B3 (d) · 1 mark · Correct name of the salt formed (zinc ethanoate)
B4 (e) · 1 mark · Appropriate observation stated (e.g., fizzing or effervescence)
Worked solution
a) The unbranched-chain carboxylic acid with two carbon atoms is ethanoic acid.
b) The molecular formula is C2H4O2.
c) Zn + 2CH3COOH → (CH3COO)2Zn + H2
d) The salt formed is called zinc ethanoate.
e) One observation is that there will be fizzing (effervescence) as hydrogen gas is released.