Aspirin is pain relieving antipyretic drug but can be used to prevent heart attack. Explain.
Aspirin is 2 - acetoxybenzoic acid. It is very effective in reducing or abolishing pain without causing impairment of consciousness, mental confusion, incordination or paralysis or some other disturbance or disorder of the nervous system. It reduces fever (antipyretics) and prevents platelet coagulation.
Due to, it has anti blood clotting action and, therefore, it is widely used to prevent heart attack.
Both antacids and antiallergic drugs are antihistamines but they cannot replace each other. Explain why?
Histamine is a chemical substance that stimulates the secretion of pepsin and hydrochloric acid in stomach. Antacids are designed to prevent the interaction of histamine with the receptors present in the stomach wall. As a result, less HCl is released in stomach.
Histamine contracts the smooth muscles in the bronchi and gut and relaxes other muscles in walls of fine blood vessels. As a result, histamine causes allergy. Antihistamines interfere with the natural action of histamine by competing with histamine for binding sites of receptor where histamine exerts its effect.
Since, antiallergic and antacids drugs work on different receptors, therefore, antihistamines remove allergy while antacids remove acidity.
What is a soft soap?
Chemical substances which concentrates at the surface of the solution or interfaces, from surface films, reduces surface tension of the solution and help in removing dirt and dust by emulsifying grease are called surfactants i.e., soap and detergents. Soaps are sodium or potassium salts of long chain fatty acids such as palmitic acid $\left(\mathrm{C}_{15} \mathrm{H}_{31} \mathrm{COOH}\right)$, stearic acid $\left(\mathrm{C}_{17} \mathrm{H}_3 \mathrm{COOH}\right)$ and linolic acid $\left(\mathrm{C}_{17} \mathrm{H}_{31} \mathrm{COOH}\right)$ Potassium salts of fatty acids such as palmitic acid, stearic acid and oleic acid are called soft soap.
Generally, potassium soap are soft to the skin so, they are named as soft soap.
If soap has high alkali content it irritates skin. How can the amount of excess alkali be determined? What can be the source of excess alkali?
A solution of soap is titrated with standard hydrochloric acid. It is an acid-base titration. In this titration, phenolphthalein is used as an indicator. During the preparation of soap, fat (i.e., glyceryl ester of fatty acid) is heated with aqueous sodium hydroxide
Thus, the source of this excess alkali (which irritates skin) is the alkali left unused when the soap is prepared by hydrolysis of fat.
Explain why some times foaming is seen in river water near the place where sewage water is poured after treatment?
Detergents have long hydrocarbon chains. If their hydrocarbon chain is highly branched, then bacteria cannot degrade this easily. Such detergents are non-biodegradable. Slow degradation of detergents leads to their accumulation.
These non-biodegradable detergents persist in water even after sewage treatment and cause foaming in rivers, ponds and their water get polluted. In order to overcome this issue branching of the hydrocarbon chain is controlled and kept to minimum.