Question

Litmus is obtained from which lichen?
A. Lecanora esculenta
B. Roccella tinctoria
C. Cladonia rangiferina
D. Cetraria islandica

Answer 1

Hint: Litmus is a dye used to indicate pH and it is obtained from lichens in many countries. It indicates pH by changing colour according to chemical reaction taking place inside also. It is also known as Sensor for pH.

Complete answer:
Litmus is a blue dye used to indicate acidic or basic strength of different solutions and it indicates the pH by changing its colour. pH is defined as “power of hydrogen” means amount or concentration of H+ ions in a test solution.
Litmus which is a mixture of dyes obtained from lichens is adsorbed onto a filter paper to make a litmus paper to perform pH test. This is the oldest method for acidity measurement.
Blue litmus paper turns to red under acidic conditions or solutions and red litmus paper turns to blue in basic or alkaline conditions. Neutral litmus paper is purple in colour. Wet litmus paper is also used for testing of water-soluble gases that can affect acidity or basicity.
If we talk about the chemistry of litmus paper, basically red litmus paper, containing weak diprotic acid and when it reacts to the basic compound, the hydrogen ions present in it start reacting with solution and the conjugate base starts forming. This conjugate base formed from the litmus paper has a colour blue, so in basic conditions a red litmus paper turns to blue colour.
Natural sources of litmus are different species of lichens. It is extracted from genus Roccella, Lencanora, Parmotrema and others in countries like South America, Algeria, Norway, etc. If we talk about particular species; these are, Roccella tinctoria, Roccella pygmaea, Roccella phycopsis, Lecanora tartarea, Variolaria dealbata, Ochrolechia parella, Parmotrema tinctorum, etc.

So, examining given options we can say, option ‘B’ is the correct option. We obtain litmus from Roccella tinctoria.

Additional information: When meiosis takes place inside a male, it will also generate four daughter cells but here parent cell is XY so it will have two cells having X chromosome and Two cells having Y chromosome.

Note:
Litmus paper is usually used to determine pH of liquids but can also be used for gases as well if the litmus paper is dampened with distilled water before exposure to the gases.