CBSE Class 10 Science Practical Skills – Properties of Acetic Acid
BASIC BUILDING CONCEPTS
The IUPAC name of acetic acid is ethanoic acid. It belongs to a group of acids called carboxylic acid. Its chemical formula is CH3COOH.
To study the following properties of acetic acid (ethanoic acid):
- Solubility in water
- Effect on litmus
- Reaction with sodium bicarbonate
Acetic acid, litmus paper, sodium bicarbonate, test tubes, water, test tube stand, lime water.
- Acetic acid is an organic acid and its 5-8% solution is called vinegar.
- It is a weak acid. It ionises partially.
- It turns blue litmus red.
- It is highly soluble in water.
- It reacts with sodium bicarbonate to liberate CO2 which turns lime water milky and the milkiness disappears if excess of CO2 is passed through the solution.
PROCEDURE, OBSERVATIONS AND INFERENCE
- Acetic acid/ethanoic acid (CH3COOH) has a pungent smell like vinegar.
- Acetic acid is miscible in water in all proportions i.e. acetic acid and water form a true solution.
- Acetic acid is acidic in nature as it turns blue litmus red.
- On reaction with sodium bicarbonate, CO2 gas is liberated.
- Do not inhale vapours of pure acetic acid directly.
- Keep the mouth of the test tube away from you and your classmates.
- Freshly prepared lime water should be used.
What is the formula and the IUPAC name of acetic acid?
The formula is CH3COOH and its IUPAC name is ethanoic acid.
Which functional group is present in acetic acid?
Carboxyl (-COOH) group is present in acetic acid.
Is acetic acid an inorganic/organic acid?
Acetic acid is an organic acid.
Is acetic acid a strong or a weak acid?
Acetic acid is a weak acid.
Give an equation to show its dissociation in water.
What happens when acetic acid reacts with ethyl alcohol in the presence of concentrated H2so4?
A fruity smell is obtained due to the formation of an ester.
Give the equation involved and name it.
What is vinegar?
Vinegar is a 5-8% solution of acetic acid in water.
Name the salt of acetic acid which is used for the preparation of methane.
What is glacial acetic acid?
Glacial acetic acid is pure acetic acid.
In the esterification reaction, what is the role of cone. H2SO4?
Conc. H2SO4 acts as a catalyst.
What is the IUPAC name of ethyl alcohol?
Its IUPAC name is ethanol.
Is acetic acid a solid, liquid or a gas at room temperature?
Acetic acid is a liquid at room temperature.
Which functional group is present in an ester?
Name a salt of a carboxylic acid used as a food preservative.
How can acetic acid be prepared?
It can be prepared by the oxidation of ethanol.
List two important uses of acetic acid.
- It is used for the manufacturing of metallic acetates, acetones, esters etc.
- It is used for coagulating rubber to latex.
NCERT LAB MANUAL QUESTIONS
Which gas is evolved when ethanoic acid reacts with sodium hydrogen carbonate?
CO2 gas is liberated when ethanoic acid reacts with sodium hydrogen carbonate.
CH3COOH(aq) + NaHCO3(s) ——-> CH3COONa(aq) + H2O(l) + CO2(g)
How will you test that the liberated gas is carbon dioxide?
Lime water turns milky when CO2 is passed through it. On passing the gas in excess, the milkiness disappears.
How will you show that ethanoic acid is acidic in nature?
The acidic nature of ethanoic acid can be shown by using blue litmus paper. On putting a drop of ethanoic acid on blue litmus paper it turns red, indicating ethanoic acid is acidic in nature.
Where do you find the use of ethanoic acid in day-to-day food products?
Ethanoic acid is the main constituent of vinegar which is used as a preservative.
What is the common name of ethanoic acid as sold in the market in the form of its dilute solution?
A dilute solution of ethanoic acid is vinegar.
What type of reaction takes place between ethanoic acid and sbdium hydroxide solution?
A neutralisation reaction occurs between ethanoic acid (an acid) and sodium hydroxide (a base).
CH3COOH(aq) + NaOH(aq) ———> CH3COONa(aq) + H2O(l)
PRACTICAL BASED QUESTIONS
Multiple Choice Questions/VSA (1 Mark)
Which of the following pairs of safety symbols are marked on the bottles of commercial acetic acid available in the laboratory?
On adding acetic acid to solid sodium hydrogen carbonate, a student observes the liberation of a [AI 2009]
(a) greenish yellow gas with a pungent smell.
(b) colourless and odourless gas.
(c) yellow coloured, odourless gas.
(d) colourless gas with smell of rotten eggs.
A student mixed some acetic acid with water. He would have observed the solution formed as [Foreign 2009]
(a) green and transparent.
(b) pink and opaque.
(c) yellow and transparent.
(d) colourless and transparent.
When sodium bicarbonate reacts with acetic acid, the gas liberated is
The odour of acetic acid is like that of
(a) burning plastic
(c) rotten eggs
In the following set-up, the gas evolved turns lime water milky. Identify ‘X’.
If we add red litmus solution to the following test tubes, the changes observed will be
(a) red, red
(b) red, blue
(c) blue, red
(d) blue, blue
2 mL of ethanoic acid was taken in each of the three test tubes A, B and C, and 2 mL, 4 mL and 8 mL water was added to them, respectively. A clear solution is obtained in [AI 2007C]
(a) test tube A only.
(b) test tubes A and B only.
(c) test tubes B and C only.
(d) all the test tubes
5 mL of acetic acid was added to equal volume of water and the mixture was shaken well for one minute and allowed to settle. The correct representation of the observation made would be as given in test tube
If pH paper is dipped in acetic acid, the colour of the strip would be
The reaction occurring between a carboxylic acid and an alcohol in the presence of cone. H2SO4 is called
Glacial acetic acid is a
(a) -18% solution of acetic acid.
(b) dehydrated solution of acetic acid.
(d) 45% solution of acetic acid.
When acetic acid reacts with X, a salt is formed which on reaction with soda lime gives a gas Y. X and Y are
(a) NaOH, C2H6
(b) Na, C2H6
(c) NaOH, CH4
(d) NaHCO3, C2H6
A student takes 5 mL acetic acid in test tube X and adds 3 mL distilled water into it. In test tube Y, he takes 5 mL distilled water and adds 3 mL acetic acid into it. After mixtures settle down, he observes
(a) colloid is formed in both test tubes
(b) homogenous mixture is formed in both test tubes
(c) colloid is formed in X and homogenous mixture in Y.
(d) homogenous mixture is formed in X and colloid in Y.
Four students observed the colour and odour of acetic acid and its reaction with sodium hydrogencarbonate. They tabulated their observations as given below.
The correct set of observation is that of student
Four students added a small amount of ethanoic acid to sodium bicarbonate. The gas evolved was tested for its behaviour with burning splinter and lime water.
They reported their observations as given below.
The correct observations have been reported by student
5 mL of ethanoic acid was taken in each of the two test tubes I and II. Blue and red litmus papers were dipped into test tube I and solid sodium bicarbonate was added to test tube II.
The following observations were reported:
A. Red litmus turned blue in I and no change was observed in II.
B. Blue litmus turned red in I and brisk effervescence was observed in II.
C. Red litmus turned blue in I and a gas of odour like vinegar evolved in II.
D. Blue litmus turned red in I and a gas which supports combustion evolved in II.
Which observation correctly represents the characteristics of ethanoic acid?
Short Answer Questions (2 Marks)
Which functional group is present in acetic acid? Name any other compound having same functional group.
Acetic acid has carboxylic acid as functional group. This functional group is also present in methanoic acid.
Give any four physical properties of acetic acid.
- It is a colourless liquid having a sour taste, and smell of vinegar.
- Its boiling point is 118 °C.
- It freezes to form colourless ice-like solid.
- It is miscible with water in all proportions.
What will you observe when a drop of acetic acid is placed on a strip of blue litmus paper and then on a red litmus paper one by one? What does it show?
Acetic acid turns blue litmus paper red but does not affect red litmus paper. This shows that acetic acid is acidic in nature.
How does acetic acid react with sodium bicarbonate? Give chemical equation for this chemical change.
Acetic acid reacts with sodium bicarbonate to evolve brisk effervescence of carbon dioxide gas.
How would you show that carbon dioxide gas is released when acetic acid reacts with sodium bicarbonate?
Pass the liberated gas through the lime water. If lime water turns milky, the evolved gas is carbon dioxide. On passing the gas in excess, the milkiness of lime water disappears.