The balanced equation for the oxidation of ethanol to ethanoic acid using sodium dichromate in acidic conditions is as follows:
$$3C_2H_5OH + Na_2Cr_2O_7 + 4H_2SO_4 \rightarrow 3CH_3CHO + Cr_2(SO_4)_3 + Na_2SO_4 + 7H_2O$$
(i) Deduce the oxidation numbers of chromium in the sodium dichromate reagent and in the chromium sulfate product - Leaving Cert Chemistry - Question c - 2010
Question c
The balanced equation for the oxidation of ethanol to ethanoic acid using sodium dichromate in acidic conditions is as follows:
$$3C_2H_5OH + Na_2Cr_2O_7 + 4H_2SO_4... show full transcript
Worked Solution & Example Answer:The balanced equation for the oxidation of ethanol to ethanoic acid using sodium dichromate in acidic conditions is as follows:
$$3C_2H_5OH + Na_2Cr_2O_7 + 4H_2SO_4 \rightarrow 3CH_3CHO + Cr_2(SO_4)_3 + Na_2SO_4 + 7H_2O$$
(i) Deduce the oxidation numbers of chromium in the sodium dichromate reagent and in the chromium sulfate product - Leaving Cert Chemistry - Question c - 2010
Step 1
Deduce the oxidation numbers of chromium in the sodium dichromate reagent and in the chromium sulfate product.
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Answer
In sodium dichromate, Na2Cr2O7, the oxidation state of chromium is +6. In chromium sulfate, Cr2(SO4)3, the oxidation state of chromium is +3.
Step 2
State the colour change observed as this reaction proceeds.
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Answer
The colour changes from orange to green during the reaction.
Step 3
Describe a test you could carry out to confirm that the organic product is an aldehyde.
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Answer
You could heat the product with Fehling's solution. A positive result would show a brick-red precipitate or a silver mirror when using Tollens' reagent, confirming the presence of an aldehyde.
Step 4
Give the name and structure of another organic compound that could be formed when ethanol is oxidised using acidified sodium dichromate.
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Answer
Another organic compound that can be formed is ethanoic acid (acetic acid), with the structure:
H O
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H--C--C--OH
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H
Alternatively, it can be represented as CH₃COOH.
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