The pH of 0.05 M − Fe ( NO 3 ) 2 solution is ( K h of Fe 2 + = 5.0 × 1 0 − 9 , lo g 2 = 0.30 )

Question

The pH of 0.05 M − Fe ( NO 3 ​ ) 2 ​ solution is ( K h ​ of Fe 2 + = 5.0 × 1 0 − 9 , lo g 2 = 0.30 )

TestHub · Accepted Answer

Identify the salt type: Fe(NO₃)₂ is a salt of a weak base (Fe(OH)₂) and a strong acid (HNO₃), so it undergoes cationic hydrolysis to produce H⁺ ions.

Formula for [H⁺]: For cationic hydrolysis, the concentration of hydrogen ions is given by $[H^{+}] = K_{h} \times C$ .

Substitute given values: $[H^{+}] = (5.0 \times 1 0^{- 9}) \times 0.05 = 2.5 \times 1 0^{- 10} = 2.5 \times 1 0^{- 5} M$ .

Calculate pH: $p H = - lo g [H^{+}] = 5 - lo g (2.5) = 5 - \frac{1}{2} lo g (\frac{10}{4})$ .

Final Computation: Using $lo g 2 = 0.30$ , we get $p H = 5 - \frac{1}{2} (1 - 2 \times 0.30) = 5 - 0.20 = 4.80$ .

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