Question

6. (i) Define a universal indicator. Mention its one use.
(ii) 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 and which one of the
solutions A and B will have a higher pH value?
(iii) Name one salt whose solution has pH more than 7 and one salt whose
solution has pH less than 7.

Answer 1

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6.(i) Universal indicator is a solution of many indicators which shows different colour changes for solutions with different pH values . it is used to predict the nature of solution.

(ii) Solution A has higher pH value

(iii) sodiumcarbonate has pH value more than 7 and Ammonium chloride has pH less than 7

Answer 2

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1. Universal Indicator is a solution of many indicators which shows different colour changes for solutions with different pH values.It is used to test whether a solution is acid or a base.It changes colour according to the pH of the acidic or basic medium.
2. Solution A gives pink color when a drop of phenolphthalein indicator is added to it, hence, it is a basic solution and pH range in between 9-10. Solution B gives red color when a drop of methyl orange is added to it, hence, it is an acidic solution and pH range in between 4-6. Therefore, solution A has higher pH value.
3. Sodium carbonate ( Na2CO3 ) solution has a pH more than 7 and Ammonium chloride ( NH4Cl ) solution has a pH less than 7. Salts with pH less than 7 or acidic salts are sodium bicarbonate (NaHCO3), sodium hydrosulfide (NaHS), sodium bisulfate (NaHSO4), monosodium phosphate (NaH²PO⁴), and disodium phosphate (Na²HPO⁴) etc.