Question

You have 1.0 L of a solution is 0.10 M in HCHO₂. Which of the following solutions below, when added to that solution, will make a buffer.

a)1.0 L of water

b)0.10 moles of NaCHO₂

c)0.1 moles of NaCl

d)0.1 moles of NaCl and 0.1 moles of NaCHO₂

e)0.1 moles of NaCH₃CO₂

Answer 1

To create a buffer solution using 1.0 L of 0.10 M HCHO₂, you should add 0.10 moles of NaCHO₂, as it contains the conjugate base needed to pair with formic acid to establish the buffer.

Step-by-step explanation:

To make a buffer solution with 1.0 L of 0.10 M HCHO₂, we need to add a solution containing its conjugate base or acid. The best choice from the given options would be option b, 0.10 moles of NaCHO₂. This is because NaCHO₂, sodium formate, provides the conjugate base (CHO₂⁻) to pair with HCHO₂ (formic acid), creating a buffer system. Adding NaCHO₂ maintains the proper balance between the weak acid and its conjugate base required for buffer action.

Option a, adding water, would simply dilute the solution without contributing to buffer capacity. Option c, adding NaCl, would not provide a conjugate acid or base, and thus would not contribute to making a buffer. Option d, adding both NaCl and NaCHO₂, would technically provide the conjugate base needed for the buffer, but the inclusion of NaCl is unnecessary for buffer formation. Option e, adding NaCH₃CO₂, introduces the conjugate base of acetic acid, which won't pair properly with formic acid to form a buffer.

Therefore, the correct answer is b) 0.10 moles of NaCHO₂ to form a functioning buffer with 0.10 M HCHO2.