Why does phenolphthalein assume pink colour in alkaline solutions?

Methyl orange shows yellow colour in alkaline solutions.

The developer used in photography is an alkaline solution of:

Two drops of phenolphthalein was added to 40 " mL of " HCl solution. When 30 " mL of " 0.1 M NaOH was added, part of the the solution turned pink, but colour disappeared on mixing the solutiion. Addition of NaOH was continued drop-wise untill a one-drop addition produced a lasting pink colour, and the colume of NaOH added was 32.56 mL. Calculate The concentration of HCl solution.

Explain why phenolphthalein is used as an indicator in acid-base titration. ""^(**"**)

Mention the colour changes observed when the following indicators are added to acids- (i) Alkaline phenolphathalein solution (ii) Methyl orange solution (iii) Neutral litmus solution

(a) Define a universal indicator . Mention its one use. (b) Solution A gives pink colour when a drop of phenolphthalein indicator is added to it. Solution B gives red colour when a drop of methyl orange is added to it. What type of solutions are A and B which one of the solutions A and B will have a higher pH value ? (c) Name one salt whose solutions has pH more than 7 and one salt whose solution has pH less than 7.

A few drops of sodium hydroxide solution are added to very slightly acidic indicators. State the change in colour in case of (1) methyl orange solution, (2) phenolphthalein solution, (3) litmus solution.

Acid-base indicators are either weak organic acids or weak organic bases. Indicator change colour in dilute solution when the hydonium ion concentration reaches a particular colour For example. Phenolphthalein is a coloureless substance in any aqueous solution with a pH less than 8.3 In between the pH range 8.3 to 10, transition of colour (colourless to pink ) takes place and if pH of solution is greater than 10 solution is dark pink. Considering an acid indicator Hln, the equilibrium involving it and its conjgate base In^(-) can be represented as : " " underset("acidic from")(HIn)hArrH^(+)underset("basic from")(In^(-)) pH of solution can be computed as : " " pH=pK_(In)+log.([IN^(-)])/([HIn]) In general, transition of colour takes place in between the pH range pK_(In+-1 Which of the following indicator is most suitable for titration of HB with strong base :

Statement-1:A solution containing S^(2-) ions gives purple / violet colour with sodium nitroprusside solution in alkaline solution. Statement-2:Sodium sulphide gives black precipitate with silver nitrate solution.

Acid-base indicators are either weak organic acids or weak organic bases. Indicator change colour in dilute solution when the hydonium ion concentration reaches a particular calur For example. Phenolphthalein is a coloureless stbstance in any aqueous solution with a pH less than 8.3 In between the pH range 8.3 to 10, transition of colour (colourless to pink ) takes place and if pH of solution is greater than 10 solution is dark pink. Considering an acid indicator Hln, the equilibrium involving it and its conjgate base In^(-) can be represented as : " " underset("acidic from")(HIn)hArrH^(+)underset("basic from")(In^(-)) pH of solution can be computed as : " " pH=pK_(In)+log.([IN^(-)])/([HIn]) In general, transition of colour takes place in between the pH range pK_(In+-1. An indicator is a weak acid and pH range is 4.0 to 6.0. If indicator in 50% ionized in a given solution then what is the inization constant of the acid ?