This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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The question asks for a precipitating agent for Group 3 metal ions in qualitative analysis. Step 1: Recall the standard grouping of cations in qualitative analysis. Cations are typically divided into five groups based on their precipitation reactions with specific reagents: Group 1: Precipitated by dilute HCl (e.g., Ag^+, Pb^2+). Group 2: Precipitated by H_2S in acidic medium (e.g., Cu^2+, Sn^2+). Group 3: Precipitated by NH_4OH (aqueous ammonia) in the presence of NH_4Cl (ammonium chloride). These ions precipitate as hydroxides (e.g., Al(OH)_3, Fe(OH)_3, Cr(OH)_3) or as sulfides (e.g., MnS, ZnS, NiS, CoS) if H_2S is also passed through the ammoniacal solution. Group 4: Precipitated by (NH_4)_2CO_3 in the presence of NH_4OH and NH_4Cl (e.g., CaCO_3, BaCO_3). Group 5: No precipitate with the above reagents (e.g., Na^+, K^+, NH_4^+). Step 2: Evaluate the given options based on the Group 3 precipitating agent. A: NH_4OH (Aqueous ammonia) is the characteristic precipitating agent for Group 3 metal ions, causing them to precipitate as hydroxides. B: HCl (Hydrochloric acid) is the precipitating agent for Group 1 metal ions. C: NaCl (Sodium chloride) provides chloride ions, which would precipitate Group 1 ions, but HCl is the standard reagent for this group. D: H_2S (Hydrogen sulfide) is the precipitating agent for Group 2 (in acidic medium) and can be used in conjunction with NH_4OH for some Group 3 ions, but NH_4OH itself is the primary reagent for the hydroxide subgroup of Group 3. Step 3: Conclude the correct option. Based on the standard qualitative analysis scheme, NH_4OH is the precipitating agent for Group 3 metal ions. The final answer is A Send me the next one 📸