Chapter 16 Chemistry in Everyday Life Solutions
Question - 21 : - Why is use of aspartame limited to cold foods and drinks?
Answer - 21 : -
Aspartame becomes unstable at cooking temperature. This isthe reason why its use is limited to cold foods and drinks.
Question - 22 : - What are artificial sweetening agents? Give two examples.
Answer - 22 : -
Artificial sweetening agents are chemicals that sweetenfood. However, unlike natural sweeteners, they do not add calories to our body.They do not harm the human body. Some artificial sweeteners are aspartame,saccharin, sucrolose, and alitame.
Question - 23 : - Name a sweetening agent used in the preparation of sweetsfor a diabetic patient.
Answer - 23 : -
Artificial sweetening agents such as saccharin, alitame,and aspartame can be used in preparing sweets for diabetic patients.
Question - 24 : - What problem arises in using alitame as artificialsweetener?
Answer - 24 : -
Alitame is a high potency sweetener. It is difficult tocontrol the sweetness of food while using alitame as an artificial sweetener.
Question - 25 : - How are synthetic detergents better than soap?
Answer - 25 : -
Soaps work in soft water. However, they are not effectivein hard water. In contrast, synthetic detergents work both in soft water andhard water.
Therefore, synthetic detergents are better than soaps.
Question - 26 : - Explain the following terms with suitable examples
Answer - 26 : -
(i) Cationic detergents
(ii) Anionic detergents and
(iii) Non-ionic detergents
Answer
(i) Cationicdetergent
Cationic detergents are quaternary ammonium salts ofacetates, chlorides, or bromides. These are called cationic detergents becausethe cationic part of these detergents contains a long hydrocarbon chain and apositive charge on the N atom.
For example: cetyltrimethylammonium bromide
(ii) Anionicdetergents
Anionic detergents are of two types:
1.Sodium alkyl sulphates: Thesedetergents are sodium salts of long chain alcohols. They are prepared by firsttreating these alcohols with concentrated sulphuric acid and then with sodiumhydroxide. Examples of these detergents include sodium lauryl sulphate (C11H23CH2OSO3−Na+)and sodium stearyl sulphate (C17H35CH2OSO3−Na+).
2.Sodium alkylbenzenesulphonates: These detergents are sodium salts of long chainalkylbenzenesulphonic acids. They are prepared by Friedel-Crafts alkylation ofbenzene with long chain alkyl halides or alkenes. The obtained product is firsttreated with concentrated sulphuric acid and then with sodium hydroxide. Sodium4-(1-dodecy) benzenesulphonate (SDS) is an example of anionic detergents.
(iii) Non-ionicdetergents
Molecules of these detergents do not contain any ions.These detergents are esters of alcohols having high molecular mass. They areobtained by reacting polyethylene glycol and stearic acid.
What are biodegradable and non-biodegradable detergents?Give one example of each.
Answer - 27 : -
Detergents that can be degraded by bacteria are calledbiodegradable detergents. Such detergents have straight hydrocarbon chains. Forexample: sodium lauryl sulphate
Detergents that cannot be degraded by bacteria are callednon-biodegradable detergents. Such detergents have highly-branched hydrocarbonchains. For example: sodium -4- (1, 3, 5, 7- tetra methyl octyl) benzenesulphonate
Question - 28 : - Why do soaps not work in hard water?
Answer - 28 : -
Soaps are sodium or potassium salts of long-chain fattyacids. Hard water contains calcium and magnesium ions. When soaps are dissolvedin hard water, these ions displace sodium or potassium from their salts andform insoluble calcium or magnesium salts of fatty acids. These insoluble saltsseparate as scum.
This is the reason why soaps do not work in hard water.
Question - 29 : - Can you use soaps and synthetic detergents to check thehardness of water?
Answer - 29 : -
Soaps get precipitated in hard water, but not in softwater. Therefore, soaps can be used for checking the hardness of water.
However, synthetic detergents do not get precipitatedeither in hard water or in soft water. Therefore, synthetic detergents cannotbe used for checking the hardness of water.
Question - 30 : - Explain the cleansing action of soaps.
Answer - 30 : -
Soap molecules form micelles around an oil droplet (dirt)in such a way that the hydrophobic parts of the stearate ions attach themselvesto the oil droplet and the hydrophilic parts project outside the oil droplet.Due to the polar nature of the hydrophilic parts, the stearate ions (along withthe dirt) are pulled into water, thereby removing the dirt from the cloth.
