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CARBON AND ITS COMPOUNDS (D)Hydrogenation of Oil–10th Science Notes and Question Bank




Text Book Question and Answers

I. Answer the following

1. Define saponification value. Why it is important?

Saponification value can be defined as the amount of potassium hydroxide or sodium hydroxide in milligrams required to neutralize the fatty acid present in one gram of oil or fat.

In the manufacture of soaps it helps to prepare soap which does not contain excess of potassium hydroxide or sodium hydroxide.

2. Write the importance of hydrogenation of oils

The hydrogenated oils will not digest easily because of low reactivity, long time consumption of such oils may lead to health problem

The foods prepared by using hydrogenated oils (called fats) do not get spoiled for longer time. Oils soon become rancid and spoil the food. This is why people prefer to use fats for frying and making of pastries.

3. How are fats different from oils?



1) Fats are solids at room temperature.

2) Fats are mostly saturated compounds.

3) Fats are chemically inactive.

4) Fats are difficult to digest.

5) Fats have a longer shelf life as they get oxidized slowly.

1) Oils are liquids at room temperature.

2) Oils are mostly unsaturated compounds.

3) Oils are chemically more active.

4) Oils are easy to digest.

5) Oils have a shorter shelf life as they are easily oxidized.


II. Fill in the blanks with suitable answers.

1. Fatty acid + glycerol ------------> fat/oil + water

2. Catalyst used for hydrogenation of oils is nickel

3. On oxidation oils become rancid

Additional Question and Answers

1. What are fatty acids?

A carboxylic acid (containing -COOH group) that has a long chain of either saturated or unsaturated hydrocarbons is called a fatty acid.

2. What are glycerides? What are glycerides commonly referred as?

Salts obtained in the reaction between fatty acids and glycerols are called glycerides.

Glycerides are commonly referred to as fat or oil.

3. What are the products formed when a fatty acid reacts with glycerol?

The reaction between a fatty acid and glycerol yields fat (oil) and water.

4. What are fats and oils chemically?

Fat and oil are the esters formed by the reaction between a long chain fatty acid and a tri-hydric alcohol such as glycerol. Fats and oils are also called glycerides or glyceryl esters.

5. What is the IUPAC name of glycerol?

The IUPAC name of glycerol is 1,2,3-propantriol. It is more commonly written as propane-1,2,3-triol

6. What is esterification? Write its equation

It is the process of extraction of fat or oil from fatty acid and glycerol is called esterification

Fatty acid + Glycerol ---------------- > Fat or oil + Water

7. Differentiate between fats and oils



They are unsaturated and liquids at room temperature

They are saturated and solids at room temperature

They are chemically reactive

They are chemically inactive

Difficult to transport

Easy to transport

Little shelf life because they undergo oxidation in air and produce foul smell

More shelf life because they do not undergo oxidation

8. Define hydrogenation of oils?

It is the process of converting unsaturated oils into saturated solids by passing hydrogen gas through them and in this process nickel is used as catalyst

The hydrogenated oils will not digest easily because of low reactivity, long time consumption of such oils may lead to health problem

9. What is rancidity? Between oils and fats, which are more prone to rancidification? Why?

The condition produced by natural oxidation of unsaturated fat present in foods and other products, marked by unpleasant odour is called rancidity.

Between oils and fats, oils are more prone to rancidification as they are unsaturated compounds. Fats are less prone to rancidity as they are saturated compounds and hence show little affinity for oxidation.

10. Explain the process of saponification?

It is the process of neutralizing the fatty acid present in the oil or fats by adding sodium or potassium hydroxide, in this process salt (NaCl) is used separate soap from glycerol

11. Which are the two steps involved in the saponification process?

The two steps involved in saponification are:

i. The hydrolysis of fat or oil into carboxylic acid and glycerol, and

ii. The neutralization of fatty acid by using a suitable alkali such as sodium hydroxide or potassium hydroxide

12. Expand PUFA’s

Poly unsaturated fatty acids

13. Oils are subjected to hydrogenation. Give reason.

People hydrogenate oils in order to convert them into fats so as to increase their shelf life.

14. What are the uses of glycerol?

a. It is used in preparation of medicines

b. It is used in the preparation of cosmetics

c. It is used in the preparation of explosives

d. It is used in the preparation of facial creams

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