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Question
Explain the following reaction with an example.
Saponification
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Solution
When an ester is heated with dilute sodium hydroxide (an alkali) solution, it gets converted back to the original alcohol and sodium salt of the original carboxylic acid. Such a reaction is known as saponification.
\[\ce{Ester + Sodium hydroxide ->[Heat] Sodium carboxylate + Alcohol}\]
E.g. Ethyl ethanoate and sodium hydroxide react to give sodium ethanoate and ethanol.
RELATED QUESTIONS
Ethanoic acid has a .................... odour.
(a) Rotten eggs
(b) Pungent
(c) Vinegar-like
(d) Mild
Consider the following comments about saponification reactions:
I. Heat is evolved in these reactions.
II. For quick precipitation of soap, sodium chloride is added to the reaction mixtures.
III. Saponification reactions are a special kind of neutralisation reactions.
IV. Soaps are basic salts of long-chain fatty acids.
The correct comments are
(a) I, II and III
(b) II, III and IV
(c) I, II and IV
(d) Only I and IV
When you add about 2 ml of acetic acid to a test tube containing an equal amount of distilled water and leave the test tube to settle after shaking its contents, what will you observe in the test tube after about 5 minutes?
(A) A white precipitate settling at its bottom
(B) A clear colourless solution
(C) A layer of water over the layer of acetic acid
(D) A layer of acetic acid over the layer of water
Draw the structure for the following compound.
Ethanoic acid
propanol into propanoic acid?
Name the process in each case and write the equations of the reactions involved.
Esters are sweet-smelling substances and are used in making perfumes. Describe an activity for the preparation of an ester with the help of a well labelled diagram. Write an equation for the chemical reaction involved in the formation of the ester. Also write the names of all the substances involved in the process of esterification.
Consider the following organic compounds:
HCHO, C2H5OH, C2H6, CH3COOH, C2H5CI
Choose two compounds which can react in the presence of conc. H2SO4 to form an ester. Give the name and formula of the ester formed.
Name the product formed and give an appropriate chemical equation for the following:
Ethanol oxidised by acidified potassium dichromate.
Acetic acid is a typical acid. Write one equation in case of its reactions with a bicarbonate.
If you take a pinch of sodium hydrogen carbonate powder in a test-tube and add drop-by-drop acetic acid to it, what would you observe immediately? List any two main observations.
Name the functional group present in the following compound:
HCOOH
A student adds 4 mL of acetic acid to a test tube containing 4 mL of distilled water. He then shakes the test tube and leaves it to settle. After about 10 minutes he observes:
(A) a layer of water over the layer of acetic acid
(B) a layer of acetic acid over the layer of water
(C) a precipitate settling at the bottom of the test tube
(D) a clear colourless solution
Explain the following term with example.
Monomer
Give the structural formula of Acetic acid.
Write three physical properties of acetic acid.
What is thr boilng point of acetic acid?
Choose the correct answer:
Select the acid which contains four hydrozen atoms in it.
Write an equation showing saponification.
Give the balanced chemical equation of the following reaction:
Oxidation of ethanol by acidified potassium dichromate.
A spatula full of sodium carbonate is taken in a test tube and 2 mL of dilute ethanoic acid is added to it.
Write a chemical equation for the reaction.
