The acid that is the best choice for preparing a pH = 2.00 buffer is HC2H3O2.
Let's understand this in detail:
A buffer is a chemical solution that can resist changes in pH when an acid or base is added. A pH buffer is a solution containing a weak acid and its conjugate base or a weak base and its conjugate acid.
A pH is a scale that measures the acidity or basicity of a solution. On a scale of 1 to 14, the pH range is from acid to base. Acidic solutions have a pH of less than 7, neutral solutions have a pH of 7, and basic solutions have a pH of more than 7.
An acid is a chemical that has a sour taste and reacts with a base or metal to form salt and water. The acid that is the best choice for preparing a pH = 2.00 buffer is HC2H3O2. This is because the dissociation constant Ka of HC2H3O2 is low, and pH value of 4.76. This means that its pKa value is 4.76. Hence, at pH 2, HC2H3O2 will behave as a weak acid, and its conjugate base will be its conjugate base, C2H3O2–.
The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation:
pH = pKa + log([A–]/[HA])
where pKa is the dissociation constant, and [A–] and [HA] are the conjugate base and acid concentrations, respectively.