A solution of 0.1 M weak base (B) is titrated with 0.1 M of a strong acid (HA). The variation of pH of the solution with the volume of HA added is shown in the figure below. What is the pK_b of the base? The neutralisation reaction is given by

$$B + HA\buildrel {} \over \longrightarrow B{H^ + } + {A^ - }$$

An acidified solution of 0.05 M Zn²⁺ is saturated with 0.1 M H₂S. What is the minimum molar concentration (M) of H⁺ required to prevent the precipitation of ZnS?

Use K_sp(ZnS) = 1.25 $$ \times $$ 10^$$-$$22 and overall dissociation constant of

H₂S, K_net = K₁K₂ = 1 $$ \times $$ 10^-21.

Consider the reaction,

A $$\rightleftharpoons $$ B

at 1000 K. At time t', the temperature of the system was increased to 2000 K and the system was allowed to reach equilibrium. Throughout this experiment the partial pressure of A was maintained at 1 bar. Given, below is the plot of the partial pressure of B with time. What is the ratio of the standard Gibbs energy of the reaction at 1000 K to that at 2000 K?

For the following reaction, the equilibrium constant K_c at 298 K is 1.6 $$ \times $$ 10¹⁷.

Fe²⁺(aq) + S^2-(aq) ⇌ FeS(s)

When equal volumes of

0.06 M Fe²⁺(aq) and 0.2 M S^{2$$ - $$}(aq)

solutions are mixed, the equilibrium concentration of Fe²⁺(aq) is found by Y $$ \times $$ 10^{$$ - $$17} M. The value of Y is .................