Q16 of 270 Page 67

What is an indicator? Name three common indicators.

Those chemical substances (dyes) which behave differently in acidic and basic medium and indicate by physical changes(colour, odour). Three common indicators are litmus, phenolphthalein and methyl orange.


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14 Complete and balance the following chemical equations:

 15 Fill in the blanks in the following sentences:

(a) Acid have a --------tasks and they turn -------litmus to --------


(b) Substance do not show their acidic properties without ----------


(c) Acids produce ------- ions on dissolving in water.


(d) Those substance whose smell (or odour) changes in acidic or basic solutions are called ------indicators.


(e) Onion and vanilla extract are ------ indicators.

 16 Name the acid-base indicator extracted from lichen. 16 What colour does the turmeric paper turn when put in an alkaline solution?