What is the pH of a 1 * 10^-3 M solution of Na3PO4? You can ignore the formation of H2PO4- and H3PO4^2-.

Verified step by step guidance

1. Identify the relevant chemical species in the solution: Na3PO4 dissociates completely in water to form 3 Na+ ions and 1 PO4^3- ion.
2. Recognize that PO4^3- is a base and can accept protons from water, forming OH- ions and HPO4^2- ions. The reaction is: \( \text{PO}_4^{3-} + \text{H}_2\text{O} \rightleftharpoons \text{HPO}_4^{2-} + \text{OH}^- \).
3. Use the base dissociation constant \( K_b \) for PO4^3- to find the concentration of OH- ions. The \( K_b \) can be calculated using the relation \( K_w = K_a \times K_b \), where \( K_w \) is the ion-product constant of water and \( K_a \) is the acid dissociation constant for the conjugate acid HPO4^2-.
4. Set up an expression for \( K_b \) using the concentrations: \( K_b = \frac{[\text{HPO}_4^{2-}][\text{OH}^-]}{[\text{PO}_4^{3-}]} \). Assume \([\text{HPO}_4^{2-}] = [\text{OH}^-] = x\) and \([\text{PO}_4^{3-}] = 1 \times 10^{-3} - x\), then solve for \( x \).
5. Calculate the pOH from the concentration of OH- ions using \( \text{pOH} = -\log[\text{OH}^-] \), and then find the pH using \( \text{pH} = 14 - \text{pOH} \).