Answer: To determine which of the given compounds will result in a solution with a pH greater than 7, we need to consider the behavior of the cation and anion in each compound in water.
Compounds that are made up of the conjugate base of a weak acid and a strong base, or a strong acid and the conjugate base of a weak base, will result in a basic solution. The conjugate base of a weak acid will hydrolyze in water, producing hydroxide ions (OH-) and resulting in an increase in pH. The conjugate base of a strong acid or a strong base will not hydrolyze, so it will not affect the pH of the solution.
With this in mind, we can identify the following compounds that will result in a solution with a pH greater than 7:
- MgF2: This compound is made up of the conjugate base of hydrofluoric acid (HF), which is a weak acid. In water, the fluoride ions will hydrolyze and produce hydroxide ions, resulting in an increase in pH.
- NH4Cl: This compound is made up of the conjugate base of ammonia (NH3), which is a weak base, and the strong acid hydrochloric acid (HCl). The chloride ions will not affect the pH of the solution, but the ammonium ions will act as a weak acid and lower the pH. However, since the question asks for compounds that will result in a pH greater than 7, NH4Cl is not the correct answer.
- Na2CO3: This compound is made up of the conjugate base of carbonic acid (H2CO3), which is a weak acid, and the strong base sodium hydroxide (NaOH). In water, the carbonate ions will hydrolyze and produce hydroxide ions, resulting in an increase in pH.
- KC2H302: This compound is made up of the conjugate base of acetic acid (CH3COOH), which is a weak acid, and the strong base potassium hydroxide (KOH). In water, the acetate ions will hydrolyze and produce hydroxide ions, resulting in an increase in pH.
Therefore, the compounds that will result in a solution with a pH greater than 7 are MgF2, Na2CO3, and KC2H302.