Questions: Determine whether or not the mixing of each pair of solutions results in a buffer. 150.0 mL of 0.15 M HCl; 135.0 mL 155.0 mL of 0.15 M NH3; 155.0 mL of 0.10 M HCl 225.0 mL of 0.10 M NH3; 250.0 mL of 0.135 M NaOH 155.0 mL of 0.15 M NH3; 175.0 mL of 0.17 M HCl

Solution Steps

A buffer solution typically consists of a weak acid and its conjugate base, or a weak base and its conjugate acid. The purpose of a buffer is to resist changes in pH when small amounts of acid or base are added.

1. 150.0 mL of 0.15 M HCl; 135.0 mL of 0.15 M NH\(_3\):

   • HCl is a strong acid.
   • NH\(_3\) is a weak base.
   • Mixing a strong acid with a weak base does not result in a buffer solution.

2. 155.0 mL of 0.15 M NH\(_3\); 155.0 mL of 0.10 M HCl:

   • NH\(_3\) is a weak base.
   • HCl is a strong acid.
   • The moles of NH\(_3\) are \(0.155 \times 0.15 = 0.02325\) moles.
   • The moles of HCl are \(0.155 \times 0.10 = 0.0155\) moles.
   • Since there is an excess of NH\(_3\) after neutralization, the solution will contain NH\(_4^+\) (conjugate acid) and NH\(_3\) (weak base), forming a buffer solution.

3. 225.0 mL of 0.10 M NH\(_3\); 250.0 mL of 0.135 M NaOH:

   • NH\(_3\) is a weak base.
   • NaOH is a strong base.
   • Mixing a weak base with a strong base does not result in a buffer solution.

4. 155.0 mL of 0.15 M NH\(_4\)Cl; 175.0 mL of 0.17 M HCl:

   • NH\(_4\)Cl provides NH\(_4^+\) (conjugate acid of NH\(_3\)).
   • HCl is a strong acid.
   • Mixing a strong acid with the conjugate acid of a weak base does not result in a buffer solution.

Final Answer