MDCAT Chemistry MCQ #2251

During qualitative salt analysis, dilute HCl is added before passing H2S gas to precipitate Group II radicals. What is the chemical purpose of HCl?

MDCAT Chemistry MCQ #2251

  1. Question 1

    Q1. During qualitative salt analysis, dilute HCl is added before passing H2S gas to precipitate Group II radicals. What is the chemical purpose of HCl?

    • A) To increase the solubility of Group II sulphides
    • B) To increase the ionization of H2S gas
    • C) To provide a basic medium for precipitation
    • D) To suppress H2S ionization via common ion effect

    Answer: To suppress H2S ionization via common ion effect

    Explanation: HCl provides a common ion (H+) that suppresses H2S ionization, allowing only Group II to precipitate. Option C fails because basicity is irrelevant.