Question

Which of these solutions is a buffer? please explain each one.

1) a 50mL solution of 1.0M HCL with a 50mL solution of 1.0M NaCl.

2) a 50mL solution of 1.0M NH₄Cl with a 10mL solution 0.05M NH_3.

3) a 50mL solution of 1.0M NH₄Cl with a 50mL solution 1.0M NaCl.

4) A 20mL solution of 1.0M HCl with a 50mL solution 1.0M NH_3.

Answer 1

a buffer solution is defined as a solution which resists any change in its pH value(i.e. whose pH remains practically constant )even when small amounts of acid or base are added to it.

1) a 50mL solution of 1.0M HCL with a 50mL solution of 1.0M NaCl will not give buffer because HCl is a strong acid and NaCl is neutral because its a salt of strong acid (HCl and strong base (NaOH) ..so the solution is mostly acidic and cannot neutralize any added acid acid so no buffer ability.

2) a 50mL solution of 1.0M NH₄Cl with a 10mL solution 0.05M NH3 will be a buffer because NH₄Cl is salt of weak base with strong acid and NH3 is a weak base.

3) a 50mL solution of 1.0M NH₄Cl with a 50mL solution 1.0M NaCl will not be a buffer because NaCl is neutral.

4) A 20mL solution of 1.0M HCl with a 50mL solution 1.0M NH3 will be a buffer because NH3 concentration is more than HCl so it will not be entirely consumed, so NH4Cl will be present and NH3 will be present so as the solution contains weak base and a salt of weak base and strong acid so it can act as a buffer solution.

NH3 + HCl ----> NH4Cl i.e. a salt of weak base and strong acid.