Carboxylic Acids

The organic compounds containing carboxylic group (–COOH) are called carboxylic acid. Common names of carboxylic acids were derived from the name of the source from which they were first extracted or obtained. IUPAC names of carboxylic acids are obtained by replacing terminal ‘e’ from the name of the corresponding alkane by the suffix ‘oic acid’. Acetic acid or ethanoic acid is a monocarboxylic acid. It is the second member of carboxylic acid family. The name acetic acid comes from the Latin word acetum and means vinegar. Vinegar commonly called as ‘Sirka’ is a dilute solution of acetic acid. Acetic acid can be prepared in the laboratory by oxidation of ethyl alcohol with potassium permanganate or potassium dichromate in acidic or alkaline medium. On large scale, acetic acid is manufacture by the oxidation of diluted solution of ethyl alcohol in the presence of ‘Acetobactor’ bacteria. Pure ethanoic acid is a colourless liquid. It has a pungent smell. It is a hygroscopic liquid and tastes sour. It is miscible with water, alcohol and ether in all proportions. Acetic acid is a weak acid that turns blue litmus red. Acetic acid can react with active metals, bases, carbonates and bicarbonates. With alcohols, acetic acid forms esters and the reaction is called as Esterification reaction. Acetic acid also undergoes dehydration, reduction and decarboxylation reactions. Sodium bicarbonate test and the ferric chloride test are the two tests used for identification of acetic acid. Acetic acid is used as vinegar, as a solvent for resins, cellulose, etc. and as a laboratory reagent. It is also used as a coagulating agent for coagulating latex in rubber industry.

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  • Q1

    The reagent which can be used to convert acetic acid into ethanol is:

    Marks:1
    Answer:

    LiAlH4

    Explanation:

    LiAlH4 (Lithium aluminium hydride) is a strong reducing agent. It reduces acetic acid to ethanol.

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  • Q2

    Acetic acid can be converted to methane by heating with

    Marks:1
    Answer:

    soda lime.

    Explanation:

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  • Q3

    A gas evolved when magnesium reacts with acetic acid is:

    Marks:1
    Answer:

    H2

    Explanation:

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  • Q4

    Acetic acid on cooling forms ice like crystals. So, it is called as

    Marks:1
    Answer:

    glacial acetic acid.

    Explanation:

    Pure acetic acid on cooling forms ice like crystals and thus appears as glacier. So, it is known as glacial acetic acid.

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  • Q5

    Vinegar

    Marks:1
    Answer:

    turns blue litmus red.

    Explanation:

    Vinegar is an aqueous solution of acetic acid. Since it is an acid, it turns blue litmus red.

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