Which of the following aqueous solutions are good buffer systems ?
. 0.26 M hydrochloric acid + 0.24 M potassium chloride
.
0.14 M acetic acid + 0.20 M potassium acetate
.
0.16 M potassium hypochlorite + 0.23 M hypochlorous acid
.
0.31 M hydrocyanic acid + 0.28 M potassium cyanide
.
0.26 M ammonium nitrate + 0.32 M ammonia
.
A good buffer consists of a weak acid and its salt OR a weak base and its salt. For example, a is not a good buffer while b is. There are others in your list that are good buffers.
To determine which of the given solutions are good buffer systems, we need to consider the properties of a buffer.
A buffer solution is a solution that can resist changes in pH when small amounts of acid or base are added to it. Buffers are usually comprised of a weak acid and its conjugate base or a weak base and its conjugate acid.
To evaluate the given solutions, we need to look for a weak acid and its conjugate base (or a weak base and its conjugate acid) in the same solution.
Let's examine each solution:
1. 0.26 M hydrochloric acid + 0.24 M potassium chloride:
- Hydrochloric acid is a strong acid, not a weak acid. Therefore, it is not suitable for a buffer system.
- Potassium chloride is not a weak base or weak acid, so it cannot act as a conjugate base or acid for hydrochloric acid.
2. 0.14 M acetic acid + 0.20 M potassium acetate:
- Acetic acid is a weak acid, which makes it a potential component of a buffer system.
- Potassium acetate is the conjugate base of acetic acid, making it a suitable partner.
3. 0.16 M potassium hypochlorite + 0.23 M hypochlorous acid:
- Potassium hypochlorite is not a weak base or weak acid, so it cannot be part of a buffer system.
- Hypochlorous acid is a weak acid, which qualifies it as a potential buffer component.
4. 0.31 M hydrocyanic acid + 0.28 M potassium cyanide:
- Hydrocyanic acid is a weak acid and can be a possible buffer component.
- Potassium cyanide is not a weak base or weak acid, so it is not suitable as a conjugate base or acid.
5. 0.26 M ammonium nitrate + 0.32 M ammonia:
- Ammonium nitrate is not a weak base or weak acid, so it cannot be part of a buffer system.
- Ammonia (NH3) is a weak base, which can be used in a buffer system along with its conjugate acid.
Based on the analysis above, the solutions that contain a weak acid and its conjugate base (or a weak base and its conjugate acid) are options 2 and 4:
Option 2: 0.14 M acetic acid + 0.20 M potassium acetate
Option 4: 0.31 M hydrocyanic acid + 0.28 M potassium cyanide
To determine whether a solution is a good buffer system, we need to check if it contains a weak acid and its conjugate base (or a weak base and its conjugate acid).
Let's analyze each option:
1. 0.26 M hydrochloric acid + 0.24 M potassium chloride: This is not a buffer system because hydrochloric acid is a strong acid, meaning it completely dissociates in water, and there is no weak acid/conjugate base pair.
2. 0.14 M acetic acid + 0.20 M potassium acetate: This is a good buffer system because acetic acid (CH3COOH) is a weak acid, and potassium acetate (CH3COOK) is the conjugate base.
3. 0.16 M potassium hypochlorite + 0.23 M hypochlorous acid: This is not a buffer system because hypochlorous acid (HOCl) is a weak acid, but potassium hypochlorite (KClO) is not its conjugate base.
4. 0.31 M hydrocyanic acid + 0.28 M potassium cyanide: This is not a buffer system because hydrocyanic acid (HCN) is a weak acid, but potassium cyanide (KCN) is not its conjugate base.
5. 0.26 M ammonium nitrate + 0.32 M ammonia: This is not a buffer system because ammonium nitrate (NH4NO3) is a salt and does not contain a weak acid and its conjugate base.
Therefore, only option 2, 0.14 M acetic acid + 0.20 M potassium acetate, is a good buffer system.