Question

The solubility of \(\text{Fe(OH)}_{3}\) is \(x\) mole per liter. Find its \(K_{sp}\).

• A. \(9x^{3}\)
• B. \(3x^{4}\)
• C. \(27x^{4}\)
• D. \(9x^{4}\)

Hint:

Write the dissolution equation, express each ion concentration in terms of x and substitute into Ksp.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept
For a sparingly soluble salt, \(K_{sp}\) is the product of the ion concentrations raised to their coefficients.

Step 2: Dissolution
\(\text{Fe(OH)}_{3}\rightleftharpoons \text{Fe}^{3+}+3\text{OH}^{-}\)
\([\text{Fe}^{3+}]=x\) and \([\text{OH}^{-}]=3x\).

Step 3: Calculation
\(K_{sp}=[\text{Fe}^{3+}][\text{OH}^{-}]^{3}=x(3x)^{3}=27x^{4}\)

Final Answer:
The Ksp of Fe(OH)3 is 27 x to the power 4. \[ \boxed{\text{(C) }27x^{4}} \]