Question

(v) To study the following properties of acetic acid (ethanoic acid): (a) Odour (b) Solubility in water (c) Effect on litmus (d) Reaction with sodium bicarbonate

Answer 1

Answer:

Explanation:

Properties of Ethanoic Acid (CH_{3}COOH)

(a) Odour : It has pungent smell

(b) Solubility in water : It is soluble in water due to formation of hydrogen bonding.

(c) Effect on litmus paper

       It turns blue litmus red, indicating that is acidic in nature.

       CH_{3}COOH\right left harpoons CH_{3}COO^{-}+H^{+}

When dissolved in H_{2}O, acetic acid undergoes dissociation to form H^{+}, ion due to release of H^{+},CH_{3}COOH is acidic in nature.

(d) Reaction with sodium hydrogen carbonate

   CH_{3}COOH+NaHCO_{3}\righ tarrow CH_{3}COONa +CO_{2}+H_{2}O

Answer 2

Answer:

EXPERIMENT – 5

Aim

To study the following properties of acetic acid (ethanoic acid):

(i) odour (smell)

(ii) solubility in water

(iii) effect on litmus

(iv) reaction with sodium bicarbonate

Theory

Acetic Acid

> The chemical name and formula of acetic acid is ethanoic acid, CH3COOH.

> The functional group — COOH group is responsible for the properties of acetic acid. —COOH is called carboxyl group.

> It is also called glacial acetic acid, because it freezes at 16.6°C.

> Acetic acid is soluble in water.

> It has vinegar like smell.

> It dissociates in water to form CH3COO and H+ ions. The dissociation is partial and hence it is called weak acid.

> It turns blue litmus red.

> It reacts with sodium bicarbonate to liberate CO2 gas.

NCERT Class 10 Science Lab Manual – Properties of Acetic Acid 3

> Acetic acid reacts with alcohol to form ester. This reaction is called esterification. Esters have fruity smell.

NCERT Class 10 Science Lab Manual – Properties of Acetic Acid 4

Materials Required

Test tubes, water, litmus paper, test tube stand, a dropper, a beaker, a cork fit in a test tube with bent tube fixed in it.

Chemicals Required: Acetic acid (ethanoic acid), Distilled water, Sodium bicarbonate and Freshly prepared lime water.

Procedure

1. Dilute the given acetic acid with distilled water in a beaker.

2. Pour 5 ml of acetic acid in a test tube and perform the following tests:

S.No. Test Experiment Observation Inference

1. Odour Take 5 mL of acetic acid in a test tube and smell it by wafting. It has a peculiar pungent smell, (vinegar like smell) Acetic acid has a vinegar like smell.

2. Solubility in water Take 2 mL of acetic acid in a test tube, add 10-15 mL of water and shake. It dissolves in water to form

homogeneous solution. Acetic acid is soluble in water in all proportions.

3. Effect on Litmus Use clean dropper and pour 1-2 drops of acetic acid on blue-litmus paper. Blue litmus paper turns red. Acetic acid turns blue litmus red.

4.  

Sodium

bicarbonate

Take a pinch of sodium bicarbonate in a clean test tube and add 1 mL of dilute acetic acid in the test tube. Reaction begins, brisk effervescence is seen, a colourless gas is evolved. Acetic acid and sodium bicarbonate react to liberate CO2 gas.

Fix a cork with bent delivery tube in the mouth of above test tube. Dip the other end of delivery tube to a test tube containing lime water. The gas turns lime water milky. CO2 gas evolved above reacts with calcium hydroxide to form calcium carbonate which is insoluble in water.

Ca(OH)2 + CO2 —> CaCO3 + H20

(White

precipitate)

Reactions

NCERT Class 10 Science Lab Manual – Properties of Acetic Acid 5

Precautions

1. Acetic acid should be handled with care.

2. The vapours of the chemicals should not be inhaled.

3. Add only small amount of NaHCO3 to ethanoic acid to control the intensity of CO2 evolved.

4. Use freshly prepared lime water for CO2 test.