Acid [pH <7] – Sour, Base [14 > pH > 7] – bitter and soapy to touch. Water soluble base –alkali.
Turmeric, litmus [obtained from lichens], China rose are some natural indicators of acid, base. Vanilla, onions and clove are olfactory indicators.
|
ACID |
OCCURS IN |
|
acetic acid |
vinegar |
|
formic acid |
ants sting |
|
citric acid |
citrus fruits like lemon, orange |
|
lactic acid |
curds |
|
oxalic acid |
spinach, tomato |
|
ascorbic acid [vit c] |
amla |
Table 1: Acids and their
natural occurances
|
|
OCCUR IN |
|
Calcium hydroxide |
lime water |
|
ammonium hydroxide |
window cleaner |
|
sodium or potassium hydroxide |
soap |
|
magnesium hydroxide |
milk of magnesia |
Table
2: Bases and their natural occurrences
Turmeric turns red with soap as soap is basic. Soap is sodium or potassium salt of long chain carboxylic acids, this forms scum with hard water. However detergents are salts of ammonium or sulphonate salts, these don’t form scum with hard water and remain effective. China rose turns dark pink for acidic and green for basic. Phenolphthalein turns colorless with acid and pink with base.
Acid reacts with base to get salt and water; heat is always evolved [exothermic]. Salt can be basic, acidic or neutral. This is called neutralization. Salts of strong base and strong acid are neutral. Those of strong acid and weak base are acidic and strong base, weak acid are basic. Blood is basic in nature.
Carbon dioxide turns lime water [calcium hydroxide] into milky [calcium carbonate]
Galvanization is depositing zinc on iron objects to prevent rusting as it cuts off contact of water vapor and oxygen with iron. Stainless steel doesn’t rust, its iron and chromium, nickel, manganese and carbon
We take milk of magnesia [base] when we get indigestion due to excess hydrochloric acid in stomach.
To remove effect of ant bite [formic acid] we put moist baking soda [sodium bicarbonate] or calamine solution [zinc carbonate]. Nettle sting releases methanoic acid.
By adding excess fertilizers soil becomes acidic so we put quick lime [calcium oxide] or slaked lime [calcium hydroxide] to it. To make it less basic we add organic matter to it.
Acid rain is caused by carbon dioxide, nitrogen dioxide and sulfur dioxide which mix with water to become nitric acid, carbonic acid and sulphuric acid. Sulphur dioxide is emitted by coal based power plants.
Bleaching
powder [calcium oxychloride] is used for bleaching
clothes and disinfecting water. Washing soda is used for
removing permanent hardness of water and as a cleaning
agent.
Plaster of Paris or calcium hemihydrates [CaSO4, ½ H2O] is used as a plaster to support fractured bones in the right position. On mixing with water it becomes gypsum [CaSO4, 2H2O] which is hard.
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