NCERT Solutions for Class 12 Chemistry Chapter 16 - Chemistry in Everyday Life

Question 1:

Sleeping pills are recommended by doctors to the patients suffering from sleeplessness but it is not advisable to take its doses without consultation with the doctor. Why ?

Answer:

Most of the drugs taken in doses higher than recommended may cause harmful effects and act as poison leading to death. Therefore, a doctor must always be consulted before taking any medicine, who will advice the patient for proper and safe doses of the drug.

Question 2:

Read the following statement :
“Ranitidine is an antacid”. With reference to which classification has this statement been given.

Answer:

This statement refers to the classification of the drugs according to pharmacological effect of the drug. This drug ranitidine is used to counteract the effect of excess acid in the stomach and therefore, will be called antacid.

Question 3:

Why do we require artificial sweetening agents?

Answer:

Artificial sweetening agents are used to reduce calorie intake. These also protect teeth from decaying.

Question 4:

Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate. Structure of these compounds are given below.

  1. (C15H31COO)3C3H5 — Glyceryl palmitate
  2. (C17H33COO)3C3H5 — Glyceryl oleate
Answer:

Question 5:

Following type of non-ionic detergents are present in liquid detergents, emulsifying agents and wetting agents. Label the hydrophilic and hydrophobic parts in the molecule. Identify the functional group(s) present in the molecule.

Answer:

Question 6:

Why do we need to classify drugs in different ways ?

Answer:

There are a large variety of drugs for different purposes of diagnosis, prevention, relief or cure of different diseases. These have been classified according to various criteria depending upon their pharmacological effect, upon their action on a particular biochemical process, on the basis of their chemical structure, on the basis of molecular targets, etc. These classification have their own usefulness. For example,

  1. Classification on the basis of pharmacological effect of the drugs is useful to doctors because it provides them the whole range of drugs available for the treatment of a particular type of disease.
  2. Classification on the basis of action of a particular biochemical process is useful for selecting the correct lead compound for designing the synthesis of a desired drug.
  3. Classification on the basis of chemical structure helps to design the drugs having similar pharmacological activity and then selecting the drug with least toxicity.
  4. Classification on the basis of molecular targets is useful for medicinal chemists so that they can design a drug which is most effective for a particular acceptor site.
Question 7:

Explain the term target molecules or drug targets as used in medicinal chemistry.

Answer:

Drugs taken by a patient interact with macromolecules such as proteins, carbohydrates, lipids and nucleic acids, and these are called drug targets. These macromolecules or drug targets are known to perform several roles in the body.

The drugs are designed to interact with specific targets so that these have least chances of effecting the other targets. This minimises the side effects and localises the action of the drug.

Question 8:

Name the macromolecules that are chosen as drug targets.

Answer:

The macromolecules which are chosen as drug targets are carbohydrates, proteins, lipids and nucleic acids.

Question 9:

Why should not the medicines be taken without consulting doctors ?

Answer:

The drugs or medicines have side effects also. In addition to normal desired therapeutic effect, drugs may also cause other effects which may be beneficial or harmful. These side effects arise because the drug may bind to more than one type of receptor. Therefore, the doctor must be consulted to choose the right drug which has maximum affinity for a particular receptor site to have the desired effect. The doctor will also advise for the correct doses because some drugs like opiates in higher doses may act as poisons leading to serious problems and even may cause death.

Question 10:

Define the term chemotherapy.

Answer:

The branch of chemistry which deals with the treatment of diseases using chemicals is called chemotherapy.

Question 11:

Which forces are involved in holding the drugs to the active site of enzymes?

Answer:

The forces holding drugs to the active sites of enzymes are hydrogen bonding, ionic bonding, dipole-dipole interactions or van der Waals interactions.

Question 12:

While antacids and antiallergic drugs interfere with the function of histamines but why do these not interfere with the function of each other ?

Answer:

Drugs designed to cure some ailments in one organ in the body do not affect the other parts because they work on different receptors. For example, secretion of histamine causes allergy. It also causes acidity due to release of excessive hydrochloric acid in the stomach. Since antiallergic and antacid drugs work on different receptors, antihistamines cure allergy while antacids remove acidity.

Question 13:

Low level of noradrenaline is the cause of depression. What type of drugs are needed to cure this problem ? Name two drugs.

Answer:

Noradrenaline induces a feeling of well being and helps in changing the mood. If the level of noradrenaline is low, then the signal sending activity of the hormone becomes low and the person suffers from depression. In such cases, the patient needs anti-depressant drugs which inhibit the enzymes which catalyse the degradation of noradrenaline. The common drugs used as anti-depressant are iproniazid and phenelzine.

Question 14:

What is meant by the term ‘broad spectrum antibiotics’ ? Explain.

Answer:

These are the antibiotics which are effective against several types of harmful micro-organisms. Therefore, these are used to cure a variety of diseases. For example, chloramphenicol is effective against a variety of diseases such as typhoid, acute fever, dysentery, whooping cough, eye infections, certain urine infections, etc. Other broad spectrum antibiotics are tetracycline, ofloxacin, etc.

Question 15:

How do antiseptics differ from disinfectants ? Give one example of each.

Answer:

Antiseptics are the chemical substances which are used to either kill or prevent the growth of micro-organisms. These are not harmful to living tissues and can be safely applied on wounds, cuts, diseased skin surfaces. For example, dettol, savlon, furacin, soframycin, etc.

Disinfectants are the chemical substances which kill micro-organisms but they cannot be applied on living tissues. In other words, they also kill micro-organisms like antiseptics but are not safe for living tissues. These are commonly applied to inanimate objects such as floor, drainage system, instruments, etc. Some common examples of disinfectants are phenol (1% solution), chlorine (0.2 to 0.4 ppm), etc.

Question 16:

Why are cimetidine and ranitidine better antacids than sodium bicarbonate or magnesium or aluminium hydroxide ?

Answer:

If excess of sodium bicarbonate, Mg(OH)2 or Al(OH)3 is used, it will make the stomach alkaline and trigger the production of even more HCl which may cause ulcers in the stomach. In contrast, cimetidine and ranitidine prevent the interaction of histamine with the receptor cells present in the stomach wall. This releases lesser amount of HCl.

Question 17:

Name a substance which can be used as an antiseptic as well as disinfectant.

Answer:

0.2% solution of phenol acts as an antiseptic while 1% solution of phenol acts as a disinfectant.

Question 18:

What are main constituents of dettol ?

Answer:

The main constituent of dettol are chloroxylenol and terpineol in a suitable solvent.

Question 19:

What is tincture of iodine ? What is its use ?

Answer:

2–3% iodine solution of alcohol-water is called tincture of iodine. It is a powerful antiseptic and is applied on wounds.

Question 20:

What are food preservatives ?

Answer:

The chemical substances which are added to the food materials to prevent their spoilage and to retain their nutritive value for long periods are called food preservatives. For example, sodium benzoate, sodium metabisulphite, etc.

Question 21:

Why is use of aspartame limited to cold foods and drinks ?

Answer:

Aspartame is unstable at cooking temperature and decomposes. Therefore, it is used as sugar substitute in cold drinks and soft drinks.

Question 22:

What are artificial sweetening agents ? Give two examples.

Answer:

The chemical substances which give sweetening effect to food but do not add any calorie to our body are called artificial sweetening agents. For example, saccharin, aspartame.

Question 23:

Name the sweetening agent used in the preparation of sweet for a diabetic patient.

Answer:

Any artificial sweetening agent such as aspartame, saccharin or alitame may be added.

Question 24:

What problem arises in using alitame as artificial sweetener ?

Answer:

Alitame is a high potency artificial sweetening agent. Therefore, it poses a problem to control the sweetness of the food.

Question 25:

How are synthetic detergents better than soaps ?

Answer:

The detergents are better than soaps because of the following reasons :

  1. Detergents can be used for washing even in hard water. On the other hand, soaps cannot be used in hard water.
  2. Detergents can be used in acidic solutions because they are not readily decomposed in acidic medium. On the other hand soaps cannot be used in acidic medium because they are decomposed into carboxylic acids in acidic medium.
  3. Detergents have a stronger cleansing action than soap.
Question 26:

Explain the following terms with suitable examples

  1. cationic detergents
  2. anionic detergents and
  3. neutral detergents.
Answer:
  1. Cationic detergents are those which have cationic hydrophilic group. These are mostly acetates, chlorides or bromides of quaternary ammonium salts. For example, cetyltrimethyl ammonium bromide :

  2. Anionic detergents are those which have anionic hydrophilic group. These are manufactured from long chain alcohols. For example, sodium lauryl sulphate : C11H23CH2OSO3Na
    Sodium p-dodecyl benzene sulphonate :

  3. Neutral detergents are esters of high molecular mass with fatty acids. These contain polar groups which can form hydrogen bonds with water. For example, polyethylene glycol stearate : CH3(CH2)16COO(CH2CH2O)n CH2CH2OH
Question 27:

What are biodegradable and non-biodegradable detergents ? Give one example of each.

Answer:

Detergents having straight hydrocarbon chains are easily decomposed by micro-organisms and are called bio-degradable detergents. e.g., sodium lauryl sulphate, sodium p-dodecyl benzene sulphonate.

The detergents having branched hydrocarbon chains are not easily decomposed by micro-organisms and are called non-biodegradable detergents e.g., sodium 4-(1,3,5,7-tetramethyloctyl) benzene sulphonate.

Question 28:

Why do soaps not work in hard water ?

Answer:

Hard water contains calcium and magnesium salts. Therefore, in hard water soap gets precipitated as insoluble calcium and magnesium soaps which being insoluble stick to the cloth as gummy mass and blocks the ability of soap to remove oil or grease from the cloth.

Question 29:

Can you use soaps and synthetic detergents to check the hardness of water?

Answer:

Soaps give insoluble precipitate of calcium and magnesium soaps in hard water whereas detergents do not give precipitate. Therefore, soaps but not detergents can be used to check the hardness of water.

Question 30:

Explain the cleansing action of soaps.

Answer:

The cleansing action of soaps and detergents follows the same principle. Soaps and detergents consist of two parts :

  1. A non-polar part which consists of long chain hydrocarbon part. It is called non-polar tail. This part is insoluble in water but soluble in oil and grease. This is also called water repelling or hydrophobic part.
  2. An ionic part which consists of carboxylate ion (in case of soaps) or sulphonates or sulphates (in case of detergents). This is called polar head. It is soluble in water but insoluble in oil or grease. The ionic part is called water attracting or hydrophilic part. Therefore, soaps and detergents consist of a large hydrocarbon tail with a negatively charged head. The hydrocarbon tail is hydrophobic (water repelling) and negatively charged head is hydrophillic (water attracting). The dirt in the cloth is due to the presence of dust particles in fat or grease which stick to the cloth. When a soap or a detergent is dissolved in water, the molecules gather together as clusters called micelles. When the dirty cloth is dipped in soap or detergent solution, the soap and dirt particles come in contact with each other. The non-polar tails of the soap begin to dissolve in non-polar oil or grease, while the polar head part remains directed in water as shown in figure. As more and more soap

    particles enter the grease, each fat or oil particle is surrounded by a number of negatively charged ends. Since the similar charges repel each other, the oil or grease droplets break off into small globules of oil. These are still surrounded by the negatively charged polar heads of the soap molecules. This prevents the small globules from coming together to form bigger particles (aggregates). The rubbing by hands or mechanical stirring also help to break the grease particles. In this manner, the grease particles can be completely broken up and it forms emulsion of grease or oil contained in dirt and water. As a result, the cloth gets free from the dirt and the droplets are washed away with water.

Question 31:

If water contains dissolved calcium bicarbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes ?

Answer:

Calcium bicarbonate makes water hard. Soap will give precipitate with this hard water and therefore, can not be used for cleaning clothes. On the other hand, a synthetic detergent does not give precipitate in hard water because its calcium salt is also soluble in water. Therefore, synthetic detergent can be used for cleaning clothes in hard water.

Question 32:

Label the hydrophilic and hydrophobic parts in the following compounds.

Answer:

Helpline