If the solubility product of iron $\left(\mathrm{III}\right)$ hydroxide is $1.8\times {10}^{-37}$, the $\mathrm{pH}$ of a saturated solution of iron $\left(\mathrm{III}\right)$ hydroxide in distilled water is close to:

The colour changes of an indicator $\mathrm{Hln}$ in acid base titrations is given below,

$\mathrm{HIn} \left(\mathrm{aq}\right)\rightleftharpoons {\mathrm{H}}^{+} \left(\mathrm{aq}\right)+{\ln }^{-} \left(\mathrm{aq}\right)$

colour $\mathrm{X}$ colour $\mathrm{Y}$

Which of the following statements is correct?

What maximum $\mathrm{pH}$ must be maintained in a saturated ${\mathrm{H}}_2\mathrm{S}$ solution $(0.1 \mathrm{M})$ to avoid precipitation of both ${\mathrm{Mn}}^{2+} \text{and} {\mathrm{Fe}}^{2+}$ from a solution, in which each ion is present at a concentration of $0.01 \mathrm{M}?$

$\left({\mathrm{K}}_{\mathrm{a}}\right.$of ${\mathrm{H}}_2\mathrm{S}=9.6\times {10}^{-21}; {\mathrm{K}}_{\mathrm{sp}}$ of $\mathrm{MnS}=2.5\times {10}^{-13}; {\mathrm{K}}_{\mathrm{sp}}$ of$\left.\mathrm{FeS}=6.4\times {10}^{-18}\right)$

What minimum $\mathrm{pH}$ must be maintained in a saturated ${\mathrm{H}}_2\mathrm{S}$ solution $(0.1 \mathrm{M})$ to avoid precipitation of both ${\mathrm{Mn}}^{2+} \text{and} {\mathrm{Fe}}^{2+}$ from a solution, in which each ion is present at a concentration of $0.01 \mathrm{M}?$

$\left({\mathrm{K}}_{\mathrm{a}}\right.$of ${\mathrm{H}}_2\mathrm{S}=9.6\times {10}^{-21}; {\mathrm{K}}_{\mathrm{sp}}$ of $\mathrm{MnS}=2.5\times {10}^{-13}; {\mathrm{K}}_{\mathrm{sp}}$ of$\left.\mathrm{FeS}=6.4\times {10}^{-18}\right)$