On passing H2S gas into first group filtrate sometimes yellow turbidity appears even in the absence — Qualitative and Quantitative Analysis Chemistry Question

💡 Solution & Explanation

Step 1: Yellow turbidity in qualitative analysis typically represents the formation of colloidal elemental sulfur. Step 2: When H2S gas is introduced into an acidic solution containing strong oxidizing anions (acid radicals) like nitrate (NO3^-), nitrite (NO2^-), or chromate (CrO4^2-), the H2S is oxidized to elemental sulfur. Step 3: Thus, the appearance of yellow turbidity is caused by the oxidation of H2S gas by these acid radicals, matching option (c).