The dark blue colour in the pH scale refers to __________.

Correct option is D

The correct answer is option (d) strong basic solution.

The dark blue color in the pH scale typically refers to a strongly basic (alkaline) solution, with a pH value of around 11 to 14.

Information booster :

Strong Acidic Solution:

• A strongly acidic solution has a pH between0 to 3.
• Examples include concentrated hydrochloric acid (HCl) or sulfuric acid (H₂SO₄).
• The solution will turn indicators such as litmus paper red, indicating the presence of a strong acid.

Weak Acidic solution:

• A weak acidic solution has a pH between 4 to 6 .·       
• Example include Acetic acid (CH₃COOH)
• Weak acids turn blue litmus paper to red

Neutral Solution:

• A neutral solution has a pH of exactly7, which is neither acidic nor basic.
• Pure water (H₂O) is an example of a neutral solution.
• It doesn't change the color of pH indicators like litmus paper, which remains unchanged.

Weak Basic Solution:

• A weak basic solution has a pH between7.1 to 8.5.
• Examples include ammonia solution (NH₃) or baking soda solution.
• It causes indicators like red litmus paper to turn slightly blue.

Strong Basic Solution:

• A strong basic solution has a pH between12 to 14.
• Examples include sodium hydroxide (NaOH) or potassium hydroxide (KOH) solutions.
• This solution will turn indicators like red litmus paper blue, with a very strong reaction near the top of the scale.
• Dark blue corresponds to pH values of 12 and above, where the solution is highly basic.