Name the acid base indicator extracted from lichen

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a) Acid-base indicators are substances that determines whether a solution is an acid or a base primarily based on change in their characteristic colour or odour. The three common indicators are:- i. Litmus paper ii. Methyl orange iii. Phenolphthalein b)Acid base indicator extracted from lichen is Litmus which further processed to make litmus paper. c) Methyl orange changes its colour from orange to red when added to an acidic solution. (A) Both acids and bases change the colour of all indicators. (B) If an indicator gives a colour change with an acid, it does not give a change with a base. (C) If an indicator changes colour with a base, it does not change colour with an acid. (D) Change of colour in an acid and a base depends on the type of the indicator. Q. Litmus, phenolphthalein and methyl orange are the common acid-base indicators. Basically these are organic dyes with characteristic colours. Litmus is the extract of the plant lichen. Phenolphthalein and methyl orange are synthesised in the laboratory. An indicator imparts a specific colour to an acidic solution and its colour changes. when the solution becomes basic or alkaline. The same applies to the basic solution as well. Will there be a color change if dilute HCl solution is slowly added to the solution of Na 2 CO 3 and few drops of methyl orange?

[2] pH = p K + log I − HI From eqn [2], it can be predicted whether the indicator is in its acid or base form, depending on the pH. The last term is the concentration ratio between the base and the acid forms of the indicator, and thus determines the color of the solution. The human eye has limited sensitivity for distinguishing the components of a mixture of colors. It can be accepted as a working rule, however, that for a mixture of two complementary colors the eye can only detect a change in hue when the concentration ratio is varied between 10 and 1/10. If these two limiting ratios are substituted into eqn [2], the well-known relation pH=p K±1 giving the color transition pH range of the acid–base indicator is obtained. This interval represents the pH region in which the acid–base indicator fully changes its color. Thus the color transition pH range is located in a pH region that depends on the protolysis constant of the indicator. A similar relationship is easily derived for an indicator of the basic type. However, the transition pH range is often not symmetrically distributed with respect to the p K value of the indicator because the spectral sensitivity of the human eye is not equal throughout the whole visible spectrum. This is why the transition interval is best defined by experiment and often reported in the literature. In Table 1 the transition pH ranges of a wide series of indicators with good quality of the color change that cover the whole useful acidity range...