[填空题]
Hydrogen sulfide,$H_2S$, is a weak acid with a $pK_a$ of 7.04.
1.1.State the acid dissociation constant expression for $H_2S$.
2.Calculate $K_a$ for $H_2S$. $\times 10^{-8}$
2.1.State the base dissociation constant expression for $HS^-$.
2.Calculate $K_b$ for $HS^-$ assuming a temperature of 298K. $\times 10^{-7}$
3.Using your answers to parts (a)(i) and (b)(i), derive the equation $K_w =K_a \times K_b$
