Acids, Bases and Salts
Acids and Bases
Sour and bitter tastes of food are due to acids and bases respectively present in them.
If a person is suffering from the problem of acidity due to overeating, then we suggest him to take baking soda solution as remedy. It is based on the fact that, acids and bases have an ability to nullify the effect of each other.
How can we decide sour and bitter substances without tasting them ?
It is possible using acid-base indicators such as litmus, phenolphthalein, methyl orange etc.
Acids are sour in taste and change the colour of blue litmus to red.
Bases are bitter in taste and change the colour of red litmus to blue.
What are Acid-Base indicators ?
Those substances which give different colors in acidic and basic mediums and indicate the presence of acid or base in a solution are called acid-base indicators. For example, litmus, phenolphthalein, methyl orange etc.
Litmus is a natural indicator. It is a purple dye which is obtained from lichen (Plant belonging to division thallophyta). When the litmus solution is neither acidic nor basic, its color is purple.
Turmeric, red cabbage leaves, coloured petals of flowers like Hydrangea, petunia, Geranium etc. are other examples of natural indicators which indicate the presence of acid or base in a solution. These are also called acid-base indicators or simply indicators.
You have noticed that, the stain of curry on a white cloth becomes reddish-brown when soap (which is basic in nature) is scrubbed on it. It turns yellow again when cloth is washed with plenty of water.
Phenolphthalein and methyl orange are the examples of synthetic acid-base indicators.
Phenolphthalein is colourless in acidic and neutral medium but gives pink colour in basic medium.
Methyl orange is red coloured in acidic medium, but gives yellow colour in basic medium.
Download MCQs on acids, bases and salts from the following link-