Question

One desires to prepare a positively charged silver iodide sol. This can be achieved by

• A. Adding a little AgNO₃ solution to KI solution in slight excess
• B. Adding a little KI solution to AgNO₃ solution in slight excess
• C. Mixing equal volumes of equimolar solutions of AgNO₃ and KI
• D. None of these

Answer 1

Answer: (B)

In the preparation of positive sol of $AgI$ , the excess of $AgNO_{3}$ is added to potassium iodide solution.
If potassium iodide is taken slight excess, negative sol of silver iodide is formed.
$KI+AgNO_{3} \rightarrow AgI+KNO_{3}AgNO_{3} \rightarrow Ag^{+}+NO_{3}^{-}AgI+Ag^{+} \rightarrow AgI/Ag^{+}$