Indicators

Define indicators. State two acid-base indicators & mention their colour change.

Ans. i) Indicators are defined as the acidic and basic nature of the compounds can also be indicated by some natural as well as chemical substances are known as indicators.

            ii) Phenolphthalein & methyl orange are two acid-base indicators.

         iii) Phenolphthalein is colourless in acid solution while it turns into pink colour in base solution.

           iv) Methyl orange gives orange colour with acid solution & yellow colour with base solution.

Name the carboxylic acids present in

Sr.No.		Acid	Sr.No.		Acid
1.	Tamarind		1.	Milk
2.	Butter		2.	Orange
3.	Roots of Plant velerum		3.	Red ants
4.	Lemon		4.	Honey bee

 Ans.     1) Tamarind – tartaric acid                              2) Butter – Butyric acid         

            3) Roots of plant velerum – Valeric acid           4) Lemon – citric acid

            5) Milk – Lactic acid                                       6) Orange – citric acid           

            7) Red ants – Formic acid                               8) Honey bee – Formic acid

Explain the term olfactory indicator.

Ans.  Substances whose odour changes in acidic or basic medium are called olfactory        indicator.

         e.g. Eucalyptus (nilgiri) Oil, Onion & clove extract.

What is universal indicator?  Does Mg OH2 react with sodium hydroxide? If not,         why?

Ans. i) Universal indicator is a mixture of several indicators which gives different colours            at different p^H values of the p^H scale.

     ii) Mg OH2 does not react with sodium hydroxide as both are bases having the same           negative radical i.e. OH-

What do you understand by universal indicator?

Ans. i) Universal indicator is a mixture of several indicators.

      ii) It has a very wide range and indicating p^H value almost from 0 to 14.

    iii) When one or two drops of universal indicator is added to a solution it changes its            colour. This colour is matched against the colour on a standard colour chart (usually     given on its bottle) to find the p^H & the p^H value can be read. This indicates the strength          of the solution.

    iv) It is available in the form of solution or in the form of paper strips.

Write a short notes on Indicators (give suitable example)

Ans. i) The acidic & basic nature of the compounds can also be indicated by some  natural as well as chemical substances. They are known as indicators.

ii) Some indicators are obtained from nature. These are called natural indicators. e.g. Litmus solution (obtained from lower plants lichen), exteracts obtained from petals of rose or hibiscus, turmeric (stem), beet root & indigo (entire plant), etc.

iii) Some manmade chemical substances are called as synthetic indicators. ex. phenolphthalein, methyl orange, eosin, etc.

iv) Indicators also indicate the p^H of a substance by its colour. Universal indicator is specially useful to show the p^H of a substance.

Chemical reactions, Chemical reaction, iron nail & burning candle, Iron, Ferrous chloride, Hydrogen gas, sodium hydroxide, aluminium ribbon, Slaked lime, bleaching powder, Bleaching powder, Calcium carbonate, Chlorine, Sodium carbonate, Sodium chloride, carbon dioxide universal indicator, hydrogen, PH, ion, Magnesium ribbon, Magnesium chloride, sodium carbonate, sodium chloride, Aluminum carbonate, Aluminium chloride, sodium bicarbonate, sodium chloride Copper oxide (basic oxide) Hydrochloride acid copper chloride salt The Acid Base Chemistry,  Acids and Bases,  Indicators, Strength of Acids & Bases,  Acids, Bases & their reactivity,  Ionization of Acids and Bases, Salts.Slaked lime, chlorine, Bleaching powder, baking soda, washing soda, sodium bicarbonate