​Physical Properties of Acids and Bases

​Some naturally occuring acids and their Chemical Formulas

​a. Vinegar (Acetic acid): CH₃COOH

b. Sour milk /Curd (Lactic acid): C₃H₆O₃

c. Orange/Lemon (Citric acid): C₆H₈O₇

d. Tamarind (Tartaric acid): C₄H₆O₆

e. Ant sting / Nettle sting (Formic Acid/Methanoic acid): HCOOH

f. Tomato (Oxalic acid): (COOH)₂

​Some Common Bases and their Uses?

​a. Sodium Flouride (NaF): Toothpaste, which we mostly use contains sodium fluoride which is slightly basic in nature.

b. Sodium Hydroxide (NaOH): In soaps, and cleaning products including detergents and washing powder

c. Sodium Bicarbonate (NaHCO₃): Sodium bicarbonate, commonly known as baking soda, is the regular item in our kitchens.

d. Magnesium Hydroxide (Mg(OH)₂): Magnesium hydroxide is the compounds that are used as anti-acid or for neutralizing the gastric acids.

​Indicators:

​An indicator is a ‘dye’ that shows a change in colour when brought in contact with acids and bases. This tells us whether the substance we are testing is an acid or base with respect to the change of colour.

​Some Common Indicators:

a. Litmus: Blue litmus paper turns red if the substance is acidic. Red litmus paper turns blue if the substance is basic or alkaline. Litmus turns red in acidic solutions and blue in basic solutions.

b. Methyl orange: Methyl orange shows red color in acidic medium and yellow color in basic medium.

c. Phenolphthalein: It turns colorless in acidic solutions and pink in basic solutions

d. Turmeric (Haldi) contains a yellow dye, which turns red in basic solutions and remains yellow in acidic or neutral soultions.

e. The red cabbage extract remains red in acidic solutions but turns green on adding to basic solutions.​

​OLFACTORY INDICATORS:-

​The term ‘olfactory’ means ‘relating to the sense of smell’. So, olfactory indicators are those substances whose smell or odour changes in acidic or basic.

Onion, vanilla extract and Clove are common olfactory indicators.