The first and second ionization constants of H₂X$\text{H}_2\text{X}$ are 2.5 × 10⁻⁸$2.5 \times 10^{-8}$ and 1.0 × 10⁻¹³$1.0 \times 10^{-13}$ respectively. The concentration of X²⁻$\text{X}^{2-}$ in 0.1 M H₂X$0.1\text{ M } \text{H}_2\text{X}$ solution is _ × 10⁻¹⁵ M$\_ \times 10^{-15}\text{ M}$. (Nearest Integer)

For the given reaction, choose the correct expression of KC$K_C$ from the following :- Fe(aq)³⁺ + SCN(aq)⁻ leftharpoons (FeSCN)(aq)²⁺$$Fe_{(aq)}^{3+} + SCN_{(aq)}^{-} \rightleftharpoons (FeSCN)_{(aq)}^{2+}$$