The balanced equation for the oxidation of ethanol to ethanal using sodium dichromate in acidic conditions is as follows: $$3C_2H_5OH + Na_2Cr_2O_7 + 4H_2SO_4 \rightarrow 3C_2H_4O + Cr_2(SO_4)_3 + Na_2SO_4 + 7H_2O$$ (i) Deduce the oxidation numbers of chromium in the sodium dichromate reagent and in the chromium sulfate product. (ii) State the colour change observed as this reaction proceeds. (iii) Describe a test you could carry out to confirm that the organic product is an aldehyde. (iv) Give the name and structure of another organic compound that could be formed when ethanol is oxidised using acidified sodium dichromate.

Leaving Cert Chemistry EXPERIMENTS: ALL: The balanced equation for the ox

The balanced equation for the oxidation of ethanol to ethanal using sodium dichromate in acidic conditions is as follows: $$3C_2H_5OH + Na_2Cr_2O_7 + 4H_2SO_4 \rightarrow 3C_2H_4O + Cr_2(SO_4)_3 + Na_2SO_4 + 7H_2O$$ (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-ethanal-using-sodium-dichromate-in-acidic-conditions-is-as-follows:--$$3C_2H_5OH-+-Na_2Cr_2O_7-+-4H_2SO_4-\rightarrow-3C_2H_4O-+-Cr_2(SO_4)_3-+-Na_2SO_4-+-7H_2O$$--(i)-Deduce-the-oxidation-numbers-of-chromium-in-the-sodium-dichromate-reagent-and-in-the-chromium-sulfate-product-Leaving Cert Chemistry-Question c-2010.png$

The balanced equation for the oxidation of ethanol to ethanal using sodium dichromate in acidic conditions is as follows: $$3C_2H_5OH + Na_2Cr_2O_7 + 4H_2SO_4 \righ... show full transcript

Worked Solution & Example Answer:The balanced equation for the oxidation of ethanol to ethanal using sodium dichromate in acidic conditions is as follows: $$3C_2H_5OH + Na_2Cr_2O_7 + 4H_2SO_4 \rightarrow 3C_2H_4O + Cr_2(SO_4)_3 + Na_2SO_4 + 7H_2O$$ (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 number of chromium is +6. In chromium sulfate (Cr₂(SO₄)₃), the oxidation number decreases to +3. This reflects the reduction of chromium during the reaction.

Step 2

State the colour change observed as this reaction proceeds.

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Answer

The colour change observed during this reaction is from orange to green. The orange colour of dichromate ions ( ext{Cr}_2 ext{O}_7^{2-}) transforms to green as chromium is reduced to ext{Cr}^{3+}.

Step 3

Describe a test you could carry out to confirm that the organic product is an aldehyde.

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Answer

To confirm that the organic product is an aldehyde, you can perform a test using Fehling's solution or ammoniacal silver nitrate (Tollen's Reagent). When heated with Fehling's solution, a brick-red precipitate of copper(I) oxide forms, indicating the presence of an aldehyde. Alternatively, using Tollen's Reagent produces a silver mirror on the test tube.

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 could be formed is ethanoic acid (acetic acid). Its structure is represented as:

    O
    ||
H - C - OH
    |
    H

It can also be represented as CH₃COOH.

Deduce the oxidation numbers of chromium in the sodium dichromate reagent and in the chromium sulfate product.

State the colour change observed as this reaction proceeds.

Describe a test you could carry out to confirm that the organic product is an aldehyde.

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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