Final answer:
Both Assertion (A) about the ionization of hydrogen sulfide being low in the presence of hydrochloric acid and Reason (I) stating that hydrogen sulfide is a weak acid are true. However, the reasoning is not the correct explanation for the assertion. The correct explanation relates to the competition for protons between the acids when in solution.
Step-by-step explanation:
The ionization of hydrogen sulfide in water is indeed low in the presence of hydrochloric acid because both are acidic, and Le Châtelier's principle suggests that the addition of a strong acid like hydrochloric acid will suppress the ionization of the weaker acid, which is hydrogen sulfide. Hydrochloric acid ionizes completely in water, contributing to a higher concentration of hydronium ions.
The given assertion that hydrogen sulfide is a weak acid is also true, as it does not ionize completely in an aqueous solution. However, this characteristic alone is not the direct explanation for the low ionization of hydrogen sulfide in the presence of hydrochloric acid.
The presence of the strong acid affects the equilibrium of the weak acid's ionization. Therefore, both Assertion (A) and Reason (I) are true, but Reason (I) is not the correct explanation of Assertion (A). Hence, the correct answer is option B: Both A and R are true and R is the correct explanation of A.