Correct Option
The correct option is 2 and 3 only.
Explanation
The pH scale measures the acidity or basicity of a solution based on the concentration of hydronium ions ($H_3O^+$). The scale typically ranges from 0 to 14. Mathematically, pH is defined as the negative logarithm of the hydronium ion concentration: $pH = -\log[H_3O^+]$.
Statement-wise Analysis:
- Statement 1 is Incorrect. A solution with a pH of 7 is considered neutral (e.g., pure water at 25°C), not strongly acidic. Solutions with a pH less than 7 are acidic, while those with a pH close to 0 are considered strongly acidic.
- Statement 2 is Correct. Solutions with a pH greater than 7 are basic (alkaline). As the pH value increases from 7 to 14, the concentration of hydroxide ions ($OH^-$) increases relative to hydronium ions, indicating an increase in basic strength.
- Statement 3 is Correct. Due to the negative logarithmic relationship ($pH = -\log[H^+]$), pH and hydronium ion concentration are inversely related. A lower pH value signifies a higher concentration of hydronium ions, indicating stronger acidity. Conversely, a higher pH value signifies a lower concentration of hydronium ions.
Key Takeaway:
The pH scale ranges from 0 (strongly acidic) to 14 (strongly basic), with 7 being neutral. pH is inversely proportional to hydronium ion concentration; therefore, lower pH indicates higher acidity, and higher pH indicates higher basicity.