Final answer:
A 0.25M solution of sodium formate is basic due to the hydrolysis reaction of formate ions with water, which produces hydroxide ions. The presence of these hydroxide ions leads to a pH greater than 7, indicating the basic nature of the solution.
Step-by-step explanation:
The question asks whether a 0.25M sodium formate solution is acidic, basic, or neutral and requires the hydrolysis equation to justify the answer. Sodium formate (HCOONa) is a salt derived from the neutralization of formic acid (a weak acid) with sodium hydroxide (a strong base). Upon dissolution in water, sodium formate dissociates completely into sodium ions (Na+) and formate ions (HCOO−). The sodium ions are considered to be spectator ions and do not participate in the reaction, so they can be ignored in the hydrolysis equation.
The hydrolysis reaction that occurs is between the formate ions and water, yielding formic acid and hydroxide ions:
HCOO− + H2O → HCOOH + OH−
As formic acid is a weak acid, water acts as a weak acid as well. However, compared to formate ions, it is significantly less basic. Hence, the formate ions are better at accepting protons from water molecules, resulting in the formation of hydroxide ions (OH−). The presence of these hydroxide ions indicates that the solution is basic. Therefore, a 0.25M sodium formate solution would be expected to have a pH greater than 7 and be basic in nature.
Check Your Learning
Understanding the hydrolysis of salts, such as sodium formate, is crucial when determining the pH of a solution and predicting how it will respond to the addition of strong acids or strong bases. This concept is pivotal in buffer systems, where a combination of a weak acid and its corresponding salt (weak base) can resist changes in pH when small amounts of other strong acids or bases are added to the solution.