Question:

A \(1.0\ L\) aqueous solution contains \(1\times 10^{-8}\ M\ NaBr\), \(1\times 10^{-8}\ M\ NaCl\) and \(1\times 10^{-8}\ M\ NaI\). To this solution, \(1\times 10^{-10}\ M\) aqueous \(AgNO_3\) solution is added drop wise. The order of precipitation of \(AgX\), where \(X=Cl, Br, I\), is
\[ K_{sp}(AgCl)=1.8\times 10^{-10} \] \[ K_{sp}(AgBr)=5\times 10^{-13} \] \[ K_{sp}(AgI)=8.3\times 10^{-17} \]

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When the concentration of anions is the same, the salt with the lowest \(K_{sp}\) precipitates first.
Updated On: Jun 18, 2026
  • \(AgBr,\ AgCl,\ AgI\)
  • \(AgCl,\ AgBr,\ AgI\)
  • \(AgI,\ AgBr,\ AgCl\)
  • \(AgBr,\ AgI,\ AgCl\)
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The Correct Option is C

Solution and Explanation

Step 1: Understand the condition for precipitation.
For precipitation of silver halide, \[ AgX(s) \] the ionic product must exceed the solubility product.
The precipitation starts when \[ [Ag^+][X^-]=K_{sp} \] Therefore, the required concentration of \(Ag^+\) for precipitation is \[ [Ag^+]=\frac{K_{sp}}{[X^-]} \]

Step 2: Note the halide ion concentrations.

The given concentrations are \[ [Cl^-]=[Br^-]=[I^-]=1\times 10^{-8}\ M \] Since all halide ion concentrations are equal, the salt with the smallest \(K_{sp}\) will require the least \([Ag^+]\) and will precipitate first.

Step 3: Compare the solubility products.

Given, \[ K_{sp}(AgCl)=1.8\times 10^{-10} \] \[ K_{sp}(AgBr)=5\times 10^{-13} \] \[ K_{sp}(AgI)=8.3\times 10^{-17} \] The order of \(K_{sp}\) values is \[ AgI<AgBr<AgCl \]

Step 4: Determine the precipitation order.

Lower \(K_{sp}\) means lower solubility and earlier precipitation.
Therefore, the order of precipitation is \[ AgI,\ AgBr,\ AgCl \]

Step 5: Final conclusion.

Hence, \[ \boxed{AgI,\ AgBr,\ AgCl} \] Therefore, the correct option is (3).
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