2. JUSTIFICACIÓN Y OBJETIVOS
4.4. Número total de insectos capturados
(b) What is the tincture of iodine? [AI SetII 2011]
28. State the reason in each of the following cases:
(i) Soaps do not work well in hard water.
(ii) Synthetic detergents are better than soaps.
[Foreign SetI 2011]
29. What are the following substances? Give one example of each one of them?
(i) Tranquillizers (ii) Food preservatives (iii) Synthetic detergents [Delhi SetI 2012]
30. Explain the following terms giving one example of each type.
(i) Antacids, (ii) Disinfectants,
(iii) Enzymes. [Delhi SetIII 2012]
31. Explain the cleaning action of soap. Why do soaps not work
in hard water? [AI SetII 2012]
a n s w e r s
1. Analgesics : The medicines which are used to relieve pains are known as analgesics.
e.g. Aspirin, novalgin, butazolidine, etc.
2. Hormones are molecules that transfer information from one group of cells to distant tissue or organ and thus control the metabolism. So they act as chemical messengers.
3. Phenol : 0.2% solution of phenol acts as antiseptic where as 1% solution acts as disinfectant.
4. Preservatives are the substances used to prevent spoilage of food due to microbial growth during storage. The most common preservatives used are sodium benzoate, sodium metabisulphite etc. Salt, sugar and oil also act as food preservatives and have been used for many years.
5. Drugs which are used to control birth rate are called antifertility drugs. e.g. Norethindrove, novestrol.
6. The antibiotic which is effective against a wide range of gram positive and gram negative becteria is known as broad spectrum antibiotic. For example, chloramphenicol.
7. Chemical substances which prevent the growth of microorganisms or kill them but are not harmful to living tissues are called antiseptics.
For example, Dettol, Savlon, etc.
8. Antiseptics are applied to the living tissues such as wounds, cuts etc. Disinfectants are applied to inanimate things like floors, drainage systems etc.
(i) Furacine, soframicine are antiseptics.
(ii) Chlorine in aqueous solution and sulphur dioxide are disinfectants.
9. Low level of noradrenaline is the cause of depression of human being.
Equanil is used for treatment.
10. Antibiotics : The medicines which are prepared from one type of microorganisms and are used to kill or prevent the growth of some other type of microorganisms are called antibiotics. These are fungi, bacteria etc. e.g.,
(i) Dysidazirine Toxic towards cancer cells.
(ii) Ampicillin is used to cure typhoid, pneumonia, soar
throat.
11. (a) Antipyretics : The medicines taken to lower the body temperature in high fever are called antipyretics.
e.g. Crocin, aspirin, paracetamol, etc.
(b) Refer Ans. 10.
12. (i) Aspirin : OCOCH 3 COOH
(ii) Paracetamol : OH
NHCOCH 3
(iii) Chloroxylenol :
CH 3 Cl H C 3 OH
13. Biodegradable detergents : Detergents having straight chain hydrocarbons are easily decomposed by micro organisms.
These are called biodegradable detergents.
Example : Sodium 4 (1, 3, 5, 7 Tetramethylocyl) benzene sulphonate.
Nonbiodegradable detergents : Detergents having highly branched hydrocarbon chains are not degraded by bacteria easily. These are called nonbiodegradable detergents.
Example : Trimethyl stearyl ammonium chloride.
14. (i) Cationic detergents which are mostly acetates or chlorides of quaternary amines e.g., Cetyltrimethyl ammonium chloride.
(ii) Tranquillizers : They act on the central nervous system and help in reducing anxiety. They help in treatment of mental diseases and in the removal of emotional distress e.g Equanil.
15. (a) The drug which prevents the interaction of histamine with the receptors present in the stomach wall are called antihistamines. They control release of acid in stomach. e.g. Synthetic drug brompheniramine (Dimetaple) and ter fenadin e (Seldane) acts as
antihistamines.
(b) Refer Ans. 3.
16. Antibiotics : These are the chemical substances, which are partly produced as metabolic products by some specific organisms (bacteria, fungi) and can destroy some other microorganisms. e.g., Penicillin.
Broad spectrum antibiotics are those antibiotics which kill or inhibit a wide range of gram positive and gram negative bacteria. On the other hand, narrow spectrum antibiotics are those antibiotics which kill or stop the growth of gram positive or negative bacteria.
Penicillin is a narrow spectrum bactericidal and tetracycline is a broad spectrum bacteriostatic antibiotic.
17. Antiseptics: These are the chemical substances used to prevent the growth of microorganisms or to kill them and are safe to be applied to living tissues. These are applied to wounds and cuts. For examples (i) iodoform (ii) tincture of iodine.
Disinfectants : These are chemical substances used to kill microorganisms in inanimate materials and are not safe to be applied to the living tissues. Examples
(i) 1% solution of phenol.
(ii) Solution of o–, m– and pcresols in soapy water is called lysol and is used as a disinfectant.
18. (i) Antacids are those substance which neutralise the excess acid and bring the pH to appropriate level in stomach.
e.g., Magnesium hydroxide and sodium bicarbonate.
(ii) Nonionic detergents are esters of long chain fatty acids with long chain alcohols. e.g.,
CH 3 (CH 2 ) 16 COO(CH 2 CH 2 O) n CH 2 CH 2 OH Ester of polyethylene glycol with stearic acid (iii) Refer Ans. 17.
19. (i) Refer Ans. 4.
(ii) Enzymes : The proteins which perform the role of biological catalysts in the body are called enzymes e.g., Trypsin, pepsin.
(iii) Detergents : Chemical substances which help in removal of fats which bind dirty materials to the fabric or skin and improve cleansing properties of water are called detergents.
20. Preparation : Alkyl hydrogen sulphate formed by treating long chain alcohols with concentrated sulphuric acid are neutralised with alkali to form anionic detergents.
CH (CH ) CH OH 3 2 10 2 H SO 2 4 CH (CH ) CH OSO H 3 2 10 2 3
Alkyl hydrogen sulphate NaOH (aq )
CH (CH ) CH OSO Na 3 2 10 2 3 – + Anionic detergents
Uses : These are mostly used (i) for household work (ii) in tooth paste.
21. (i) Refer Ans. 10.
(ii) Refer Ans. 7.
(iii) Refer Ans. 1.
22. Analgesic medicines : The chemical substances which are used to relieve pain are called analgesic medicines.
There are two types of analgesic medicines.
(i) Non narcotic drugs : These are effective in relieving skeletal pain, preventing heart attack and viral inflammation etc.
(ii) Narcotic drugs : These are recommended for the relief in postoperative pain, cardiac pain, terminal cancer, and child birth. These are morphine derivatives and habit forming.
23. (i) Refer Ans. 19 (iii).
Example : Sodium dodecylbenzene sulphonate.
(ii) Refer Ans. 4.
(iii) Refer Ans. 18 (i).
24. (i) Artificial sweetening agents are chemical substances which are sweet in taste but do not add calories to our body.
(ii) Refer Ans. 19 (ii).
(iii) Refer Ans. 1.
25. (i) Hard water contains Mg 2+ and Ca 2+ ions which form insoluble salt with soap. That is why soap does not work in hard water.
(ii) The main constituents of dettol are terpineol and chloroxylenol.
(iii) Refer Ans. 8.
26. (i) Refer Ans. 4.
(ii) Refer Ans. 19 (iii).
(iii) Refer Ans. 18 (i).
27. (i) Refer Ans. 8.
(ii) A 23% solution of iodine in alcohol water mixture is known as tincture of iodine. It is used as an antiseptic.
28. (i) Refer Ans. 25 (i).
(ii) Synthetic detergents can be used in hard water as well as in acidic solutions. Hence those are better than soaps.
29. (i) Refer Ans. 14 (ii).
(ii) Refer Ans. 4.
(iii) Refer Ans. 19 (iii).
30. (i) Refer Ans. 18 (i).
(ii) Disinfectants are the chemicals which either kill or prevent the growth of microorganisms but are not safe for the living tissues. Disinfectants are applied to inanimate objects like floors, drains etc.
e.g. (a) Aqueous solution of ch lor in e in th e concentration 0.2 to 0.4 ppm is disinfectant.
(b) Sulphur dioxide in ver y low concentr ation is disinfectant. Some substances can act as an antiseptics at low concentration and as disinfectant at high concentration.
e.g. 0.2 percent solution of phenol is an antiseptic while its one percent solution is disinfectant.
OH
Cl H C 3 CH 3
Chloroxylenol
CH 3
H C 3 OH CH 3 Terpineol OH
Cl
Cl
S
Cl OH
Cl Bithional
(iii) Refer Ans. 19 (ii).
31. Soap is sodium or potassium salt of a higher fatty acid and may be represented as RCOO – Na + (e.g., sodium stearate CH 3 (CH 2 ) 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 nonpolar ‘tail’) which is hydrophobic (water repelling), and a polar group COO – (also called polar ionic ‘head’), which is hydrophilic (water loving).
Stearate ion Water
(a) (b)
OOC
OOC OOC OOC
COO
COO COO
COO COO CO
O
Ionic micelle
The RCOO – ions are, present on the surface with their COO – groups in water and the hydrocarbon chains R staying away from it. At critical micelle concentration, the anions are pulled into the bulk of the solution of aggregate to form a spherical shape. 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 is in the oil droplet and hydrophilic part 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.
(a) (b)
(c)
Hard water contains calcium and magnesium ions. These ions form insoluble calcium and magnesium salts when sodium or potassium soaps are dissolved in hard water.
These insoluble soaps separate as scum in water and are useless as cleansing agent.