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NCERT Solutions for Class 12 Chemistry Chapter 16 Chemistry in Everyday Life
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 ?
Most of the dru gs taken in doses higher than recommended may cause harmful effect and act as poison. Therefore, a doctor should always be consulted before taking medicine.
With reference to which classification has the statement, “ranitidine is an antacid” been given?
This statement refers to the classification according to pharmacological effect of the drug because any drug which will be used to counteract the effect of excess acid in the stomach will be called antacid.
Why do we require artificial sweetening agents?
Those people who have diabetes or who need to control intake of calories, they cannot take sugar. They need its substitute. These substitutes are called artificial sweeteners. These are excreted from the body in urine unchanged.
Write the chemical equation for preparing sodium soap from glyceryloleate and glyceryl palmitate. Structural formulae of these compounds are given below.
- (C15H31COO)3C3H5 – Glyceryl palmitate
- (C17H33COO)3C3H5 – Glyceryl oleate.
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.
The functional groups present in the molecule are alcoholic group and ethereal linkage (—O—).
Why do we need to classify drugs in different ways?
In a general way, the drug may be defined as a substance used in the prevention, diagnosis, treatment or cure of diseases. We must classify the drug so as to understand its action on our body. Drugs are classified on the basis of (a) pharmacological effect, (b) drug action, (c) chemical structure and (d) molecular targets.
Explain the term, target molecules or drug targets as used in medicinal chemistry.
Drugs usually interact with biomolecules, such as carbohydrates, lipids, proteins and nucleic acids. These are called target molecules or drug targets. These perform various functions in the body. For example, proteins which perform the role of biological catalysts in the body are called enzymes and those which are crucial to communication system in the body are called receptors. Nucleic acids have coded genetic information for the cell. Lipids and carbohydrates are structural parts of the cell membrane.
Name the macromolecules that are chosen as drug targets.
Macromolecules of biological origin such as carbohydrates, lipids, proteins and nucleic acids.
Why should not medicines be taken without consulting doctors?
Drugs are designed to interact with specific targets so that these have the least chance of affecting other targets. Only a doctor can diagnose a disease properly and prescribe the correct medicine in proper dose because excess of medicines may have harmful effects on our body. So we should not take medicines without consulting doctors.
Define the term chemotherapy.
Chemotherapy (literally means chemical treatment) is the science in which chemicals are used for the treatement of diseases. Chemotherapy is defined as the use of chemicals (drugs) to injure or destroy infectious microorganisms without causing any injury to the host. Chemotherapy has developed into a vast subject today and efforts are being continuously made to search new drugs as to free human beings from various types of diseases.
Which forces are involved in holding the drugs to the active site of enzymes?
Substrates bind to the active site of the enzyme through a variety of interactions such as ionic bonding, hydrogen bonding, van der Waals interaction or dipol-dipole interaction.
While antacids and antiallergic drugs interfere with the function of histamines, why do these not interfere with the function of each other?
Histamine stimulates the secretion of pepsin and hydrochloric acid in the stomach. The drug cimetidine (antacid) was designed to prevent the interaction of histamine with the receptors present in the stomach wall. This resulted in release of lesser amount of acid. Antacid and antiallergic drugs work on different receptors.
Low level of noradrenaline is the cause of depression. What type of drugs are needed to cure this problem? Name two drugs.
Noradrenaline is one of the Neurotransmitters that plays a role in mood changes. If the level of noradrenalines remains low for some reason, then the signal¬sending activity becomes low and the person suffers from depression. In such situations, antidepressant drugs are required. These drugs inhibit the enzymes which catalyse the degradation of noradrenaline. If the enzyme is inhibited, this important neurotransmitter is slowly metabolised and can activate its receptor for longer periods of time, thus counteracting the effect of depression. Iproniazid and phenylzine are two such drugs.
What is meant by the term ‘broad spectrum antibiotics’? Explain.
The range of bacteria or other microorganisms that are affected by a certain antibiotic is expressed as its spectrum of action. Antibiotics which kill or inhibit a wide range of Gram-positive and Gram-negative bacteria are said to be broad spectrum antibiotics, e.g., Chloramphenicol, Tetracycline, etc.
How do antiseptics differ from disinfectants? Give one example of each.
Antiseptics and disinfectants are the chemicals which either kill or prevent the growth of microorganisms. Antiseptics are applied to the living tissues such as wounds, cuts, ulcers and diseased skin surfaces. Examples are furacine, soframicine, etc. These are not ingested like antibiotics. On the other hand, disinfectants are applied to inanimate objects such as floors, drainage system, instruments, etc.
Same substances can act as an antiseptic as well as disinfectant by varying the concentration. For example, 0.2% solution of phenol is an antiseptic while its 1% solution is disinfectant.
Why are cimetidine and ranitidine better antacids than sodium hydrogencarbonate or magnesium or aluminium hydroxide?
Excessive hydrogencarbonate can make the stomach alkaline and trigger the production of even more acid. Metal hydroxides are better alternatives because being insoluble, these do not increase the pH above neutrality. These treatments control only symptoms, and not the cause. Therefore, with these metal salts, the patients cannot be treated easily.
The drugs cimetidine (Tegamet) and ranitidine (Zantac) prevent the interaction of histamine with the receptors present in the stomach wall. This resulted in release of lesser amount of acid.
Name a substance which can be used as an antiseptic as well as disinfectant.
0.2% solution of phenol is an antiseptic while its 1% solution is disinfectant.
What are the main constituents of dettol?
Dettol is a mixture of chloroxylenol (4-chloro-3,5-dimethylphenol) and terpineol.
What is tincture of iodine? What is its use?
2-3% solution of iodine in alcohol- water mixture is known as tincture of iodine. It is a powerful antiseptic.
What are food preservatives?
Food preservatives prevent spoilage of food due to microbial growth or these may be defined as the substances which are capable of inhibiting the process of fermentation, acidification or any other decomposition of food. The most commonly used preservatives include table salt, sugar, vegetable oils and sodium benzoate. Salts of sorbic acid and propanoic acid are also used as preservatives.
Why is use of aspartame limited to cold foods and drinks?
Use of aspartame is limited to cold foods and soft drinks because it in unstable to heat and decomposes at cooking temperature.
What are artificial sweetening agents? Give two examples.
The chemical substances which give sweetening effect to food but do not add any calorie to our body are celled artificial sweetening agents, e.g., aspartame, saccharin etc.
Name the sweetening agent used in the preparation of sweets for a diabetic patient.
Saccharin is of great value of diabetic persons and people who need to control intake of calories because it is excreted from the body in urine unchanged and appears to be entirely inert and harmless when taken.
What problem arises in using alitame as artificial sweetener?
Alitame is high potency sweetener (2000 times as sweet as cane sugar). The control of sweetness of food is difficult while using it.
How are synthetic detergents better than soaps?
Soaps when used in hard water form insoluble precipitates which separate as scum in water and are useless as cleansing agent. In fact these are hindrance to good washing, because the precipitate adheres onto the fibre of the cloth as gummy mass. On the other hand, synthetic detergents can be used both in soft and hard water as they give foam even in hard water. Some of the detergents give foam even in ice cold water.
Explain the following terms with suitable examples
(i) cationic detergents
(ii) anionic detergents and
(iii) non-ionic detergents.
(i) Cationic detergents : Cationic detergents are quarternary ammonium salts of amines with acetates, chlorides or bromides as’ anions. Cationic part possess a long hydrocarbon chain and a positive charge on nitrogen atom. Hence, these are called cationicdetergents.Cetyltrimethylammonium bromide is a popular cationic detergent and is used in hair conditioners.
Cationic detergents have germicidal properties and are expensive, therefore these are of limited use.
(ii) Anionic detergents : Anionic detergents are sodium salts of sulphonated long chain alcohols or hydrocarbons. Alkyl hydrogensulphates formed by treating long chain alcohols with concentrated sulphuric acid are neutralised with alkali to form anionic detergents. Similarly alkyl benzene sulphonates are obtained by neutralising alkyl benzene sulphonic acids with alkali.
In anionic detergents, the anionic part of the molecule is involved in the cleansing action. Sodium salts of alkylbenzenesulphonates are an important class of anionic detergents.
They are mostly used for household work. Anionic detergents are also used in toothpastes.
(iii) Non-ionic detergents : Non-ionic detergents do not contain any ion in their constitution. One such detergent is formed when stearic acid reacts with polyethyleneglycol.
Liquid dishwashing detergents are non-ionic type.
What are biodegradable and non-biodegradable detergents? Give one example of each.
Biodegradable detergents : Detergents having straight hydrocarbon chains are easily degraded by microorganisms and hence are called biodegradable detergents, e.g.,
Non-biodegradable detergents : Detergents containing branched hydrocarbon chains are not easily degraded by the microorganisms and hence are called non-biodegradable detergents.
Why do soaps not work in hard water?
Hard water contains calcium and magnesium ions. These ions form insoluble calcium and magnesium soaps respectively when sodium or potassium soaps are dissolved in hard water.
These insoluble soaps separate as scum in water and are useless as cleansing agent. In fact these are hindrance to good washing, because the precipitate adheres onto the fibre of the cloth as gummy mass.
Can you use soaps and synthetic detergents to check the hardness of water?
Soaps and detergents can be used to check the hardness of water. Hard water forms curdy white precipitate with Ca2+ and Mg2+ ions present in hard water whereas no such precipitates are formed by detergents in hard water.
Explain the cleansing action of soaps.
Soap is sodium or potassium salt of a higher fatty acid and may be represented as RCOO– Na (e.g., sodium stearate CH3(CH2)16 COO– Na+ When dissolved in water, it dissociates into RCOO– and Na+ ions. The RCOO– ions, however, consist of two parts – a long hydrocarbon chain R (also called non-polar ‘tail’) which is hydrophobic (water repelling), and a polar group COO- (also called polar-ionic ‘head’), which is hydrophilic (water loving).
The RCOO– ions are, therefore, present on the surface with their COO– groups in water and the hydrocarbon chains R staying away from it and remain at the surface. But at critical micelle concentration, the anions are pulled into the bulk of the solution and aggregate to form a spherical shape with their hydrocarbon chains pointing towards the centre of the sphere with COO– part remaining outward on the surface of the sphere. An aggregate thus formed is known as ‘ionic micelle’. These micelles may contain as many as 100 such ions.
The cleansing action of soap is due to the fact that soap molecules form micelle around the oil droplet in such a way that hydrophobic part of the stearate ions is in the oil droplet and hydrophilic part projects out of the grease droplet like the bristles. Since the polar groups can interact with water, the oil droplet surrounded by stearate ions is now pulled in water and removed from the dirty surface. Thus soap helps in emulsification and washing away of oils and fats. The negatively charged sheath around the globules prevents them from coming together and forming aggregates.
If water contains dissolved calcium hydrogen carbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes?
Label the hydrophilic and hydrophobic parts in the following compounds.
- CH3(CH2)15 N+ (CH3)3 Br
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