What volume of $$0.2 \mathrm{~M}$$ Acetic acid is to be added to $$100 \mathrm{ml}$$ of $$0.4 \mathrm{M}$$ Sodium acetate so that a Buffer solution of $$\mathrm{pH}$$ equal to 4.94 is obtained? $$(\mathrm{pK}_{\mathrm{a}}$$ of $$\mathrm{CH}_3 \mathrm{COOH}=4.76)$$

$$\mathrm{A}_3 \mathrm{~B}_4$$ is a sparingly soluble salt with a solubility of $$\mathrm{s} g / \mathrm{L}$$. If the Molar mass of $$\mathrm{A}_3 \mathrm{~B}_4$$ is $$\mathrm{Mg} / \mathrm{mol}$$, what is the expression for its $$\mathrm{K}_{\text {sp }}$$ ?

$$300 \mathrm{ml}$$ of an aqueous solution of $$\mathrm{NaOH}$$ with $$\mathrm{pH}$$ value of 10 is mixed with $$200 \mathrm{ml}$$ of an aqueous solution of $$\mathrm{HCl}$$ with a $$\mathrm{pH}$$ value of 4. What will be the $$\mathrm{pH}$$ of the resultant solution at room temperature?

In a $$0.2 \mathrm{~M}$$ aqueous solution, lactic acid is $$6.9 \%$$ dissociated. The value of dissociation constant is