Question

Red litmus paper turns blue in the solution the pH can be :

• A. 1
• B. 4
• C. 5
• D. 8

Hint:

Litmus Paper and pH:
{Acidic solution (pH<7):} Turns Blue litmus \(\rightarrow\) Red. Red litmus stays Red.
{Neutral solution (pH = 7):} No change in litmus color.
{Alkaline/Basic solution (pH>7):} Turns Red litmus \(\rightarrow\) Blue. Blue litmus stays Blue. The question says: Red litmus turns Blue. This means the solution is {Alkaline (Basic)}. So, we need a pH value>7. From the options, only pH = 8 is>7.

Answer 1

The Correct Option is D

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 \(\rightarrow\) 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.