Determine the pH of each solution. a. 0.20 M KCHO₂ b. 0.20 M CH₃NH₃I c. 0.20 M KI

Verified step by step guidance

1. Step 1: Identify the nature of each compound in the solution. KCHO_2 is a salt of a weak acid (HCHO_2, formic acid) and a strong base (KOH), CH_3NH_3I is a salt of a weak base (CH_3NH_2, methylamine) and a strong acid (HI), and KI is a salt of a strong acid (HI) and a strong base (KOH).
2. Step 2: For KCHO_2, determine the pH by considering the hydrolysis of the formate ion (CHO_2^-). Use the formula for the hydrolysis of anions: \( K_b = \frac{K_w}{K_a} \) where \( K_w \) is the ion-product constant of water and \( K_a \) is the acid dissociation constant of formic acid. Calculate \( [OH^-] \) and then find pOH and pH.
3. Step 3: For CH_3NH_3I, determine the pH by considering the hydrolysis of the methylammonium ion (CH_3NH_3^+). Use the formula for the hydrolysis of cations: \( K_a = \frac{K_w}{K_b} \) where \( K_b \) is the base dissociation constant of methylamine. Calculate \( [H^+] \) and then find pH.
4. Step 4: For KI, recognize that it is a neutral salt formed from a strong acid and a strong base, so it does not affect the pH of the solution. The pH of the solution is neutral, which is 7 at 25°C.
5. Step 5: Summarize the pH values: KCHO_2 solution will be basic, CH_3NH_3I solution will be acidic, and KI solution will be neutral.