WHAT IS PH SCALE AND WHAT DOES A PH OF 7 INDICATE? (CBSE 10TH CHEMISTRY)

 What is the pH Scale?

• The pH scale is a numeric scale ranging from 0 to 14 used to specify the acidity or basicity (alkalinity) of an aqueous solution.
• pH stands for "potential of Hydrogen" or "power of Hydrogen".

• It measures the concentration of hydrogen ions (H⁺) in a solution.

• The formula used:

  pH=−log10​[H+]

pH Scale Values and Their Meaning:

pH Value	Type of Solution	Examples
0–3	Strongly acidic	Hydrochloric acid, Sulphuric acid
4–6	Weakly acidic	Vinegar, Lemon juice
7	Neutral	Pure water, sodium chloride solution
8–10	Weakly basic (alkaline)	Baking soda, soap solution
11–14	Strongly basic	NaOH, KOH

• $$What\; Does\; a\; pH\; of\; 7\; Indicate?$$

• A pH of 7 means the solution is neutral.

• It has equal concentration of H⁺ and OH⁻ ions.

• It is neither acidic nor basic.

• Example: Pure water at 25°C has a pH of 7.

Additional Key Points:

• Acidic solutions have more H⁺ ions → lower pH.

• Basic solutions have more OH⁻ ions → higher pH.

• Indicators like litmus, methyl orange, and phenolphthalein help detect acidity/basicity.

• Universal indicator gives a color-coded pH value.