What is the concentration of lithium ions in a 0.400 M solution of LiHPO_4?

• A. 0.100 M
• B. 0.400 M
• C. 0.200 M
• D. 0.800 M

Answer: (B)

Verified step by step guidance

1. Identify the chemical species involved: LiHPO_4 is a salt that dissociates in water into lithium ions (Li\^+) and hydrogen phosphate ions (HPO_4\^{2-}).
2. Write the dissociation equation for LiHPO_4 in water: \(\text{LiHPO}_4 (aq) \rightarrow \text{Li}^+ (aq) + \text{HPO}_4^{2-} (aq)\).
3. Recognize that the dissociation of LiHPO_4 is complete because it is a salt of a strong base (LiOH) and a weak acid (H_3PO_4), so it fully dissociates in solution.
4. Since the dissociation produces one lithium ion per formula unit of LiHPO_4, the concentration of lithium ions will be equal to the initial concentration of LiHPO_4.
5. Therefore, the concentration of Li\^+ ions in the solution is equal to the initial concentration of LiHPO_4, which is 0.400 M.