Concept: Litmus paper is an acid-base indicator. The pH scale measures the acidity or alkalinity (basicity) of a solution.
pH<7: Acidic solution
pH = 7: Neutral solution
pH>7: Alkaline (basic) solution Litmus paper changes color depending on the pH:
Red litmus paper turns blue in an alkaline (basic) solution.
Blue litmus paper turns red in an acidic solution.
In a neutral solution, red litmus stays red, and blue litmus stays blue. Step 1: Interpret the litmus paper color change
The problem states that "Red litmus paper turns blue in the solution."
This color change (red litmus blue) indicates that the solution is alkaline (basic). Step 2: Relate alkalinity to pH value
An alkaline (basic) solution has a pH value greater than 7. Step 3: Analyze the given pH options
(1) pH = 1: This is less than 7, so it's a strongly acidic solution. (Red litmus would stay red).
(2) pH = 4: This is less than 7, so it's an acidic solution. (Red litmus would stay red).
(3) pH = 5: This is less than 7, so it's an acidic solution. (Red litmus would stay red).
(4) pH = 8: This is greater than 7, so it's an alkaline (basic) solution. (Red litmus would turn blue). Step 4: Identify the pH value that corresponds to an alkaline solution
The pH value that indicates an alkaline solution (where red litmus turns blue) is pH = 8. Therefore, the pH of the solution can be 8.