The solution of which one of the following will have pH less than 7?
NaOH
KCl
FeCl₃
NaCl
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-2 – 2018
A) NaOH (Sodium hydroxide) is a strong base. Its solution is alkaline (pH > 7).
B) KCl (Potassium chloride) is a salt formed from a strong acid (HCl) and a strong base (KOH). Its solution is neutral (pH ≈ 7).
C) FeCl₃ (Iron(III) chloride) is a salt formed from a weak base (Fe(OH)₃) and a strong acid (HCl). When dissolved in water, metal ions with high charge density, like Fe³⁺, undergo hydrolysis, reacting with water to produce hydrated metal ions and release H⁺ ions, making the solution acidic: FeCl₃(aq) + 3H₂O(l) ⇌ Fe(OH)₃(s) + 3H⁺(aq) + 3Cl⁻(aq). Therefore, its solution will have a pH less than 7.
D) NaCl (Sodium chloride) is a salt formed from a strong acid (HCl) and a strong base (NaOH). Its solution is neutral (pH ≈ 7).