when a student adds red litmus to an aqueous solution, the red litmus turned blue .which one of the following should be added in excess so that the change in colour is reversed ?
Answers
the solution must be alkaline..... so u have to add acid to make solution acidic and reverse the colour change
Answer:
The solution to be added should be acidic.
Example of acid solutions include; vinegar ( contains acetic acid), Citrus juice ( contains hydrochloric acid), sulphuric acid or nitric acid
-------------------------------------------------------------------------------------------------------------------------
Explanation:
Litmus paper is an acid-base indicator that is used to tell acidic and basic solutions apart.
Red litmus paper turns blue when placed in a basic (alkaline) solution, while blue litmus paper turns red when in an acidic solution.
The colour red on a litmus paper will appear in solutions that have a pH of less than 4.5 while the blue colour shows on pH that is 8.3 and above.
--------------------------------------------------------------------------------------------------------------------------
Having this in mind, you definitely know that the student placed the red litmus paper in an alkaline/basic solution and therefore the litmus paper turned blue.
To reverse the colour of the litmus paper to red, the aqueous solution needs to be acidic ( or the pH of the solution needs to be lowered).
Therefore the student needs to add excess of an acidic solution to make turn the colour back to red.
-------------------------------------------------------------------------------------------------------------------------