100 mL of each of the following solutions is mixed; which one of the mixed solutions is a buffer?
A) 1.0 M NH3(aq) + 0.6 M KOH(aq)
B) 1.0 M NH4Cl(aq) + 1.0 M KOH(aq)
C) 1.0 M NH3(aq) + 0.4 M HCl(aq)
D) 1.0 M NH4Cl(aq) + 0.4 M HCl(aq)
E) 1.0 M NH3(aq) + 1.0 M HCl(aq)
I am unsure how to start this problem?
Look at C.
NH3 + HCl ==> NH4Cl + H2O
initial moles:
NH3 = 1.0 M x 100 mL (0.1 L) = 0.1 mole
HCl = 0.4 M x 100 mL (0.1 L) = 0.04 mole
NH4Cl and water = 0
Since this is an acid base system and since HCl is a strong acid, it will react completely.
Final moles:
NH4Cl = 0.0.04
HCl = 0 (all of the 0.04 is used).
NH3 = 0.1-0.04 = 0.06 remaining, so what do we have?
We have a weak base (NH3) and its salt (NH4Cl). Do any of the others produce anything like that?
You can determine the concns if you wish from concn = moles/L and the final volume is 200 mL or 0.2 L.
Check my arithmetic. Sometimes I slip a decimal point when going between moles and molarity mostly because I do these in my head and work with millimoles and not moles.
Well, to determine which solution is a buffer, we need to look for a combination of an acidic and a basic component.
In options A and B, we have KOH, which is a strong base, so these options don't have a basic component.
In options C and D, we have HCl, which is a strong acid, so these options don't have an acidic component.
Option E has NH3, which is a weak base, and HCl, which is a strong acid. So this option looks promising!
However, to be a buffer, the concentrations of the acidic and basic components need to be relatively equal. In option E, the concentrations are both 1.0 M, so this satisfies the requirement for a buffer!
Therefore, option E (1.0 M NH3(aq) + 1.0 M HCl(aq)) is the buffer solution.
Hope that helps, and remember, chemistry can be quite acidic, but don't be too basic with your answers!
To determine which one of the mixed solutions is a buffer, we need to identify a weak acid and its conjugate base, or a weak base and its conjugate acid, in the mixture. Remember, a buffer solution consists of a weak acid-base pair that resists changes in pH when small amounts of acid or base are added.
Let's analyze each option step-by-step:
A) 1.0 M NH3(aq) + 0.6 M KOH(aq)
NH3 is a weak base, but KOH is a strong base. Therefore, this solution does not contain a weak acid or weak base-conjugate acid pair. Hence, it is not a buffer.
B) 1.0 M NH4Cl(aq) + 1.0 M KOH(aq)
NH4Cl is a salt, not a weak acid or weak base. KOH is a strong base. Therefore, this solution does not contain a weak acid or weak base-conjugate acid pair. Hence, it is not a buffer.
C) 1.0 M NH3(aq) + 0.4 M HCl(aq)
NH3 is a weak base, and HCl is a strong acid. Since both a weak base (NH3) and its conjugate acid (NH4+) are present, this solution can act as a buffer. NH3 will react with HCl to form NH4+ and Cl-, maintaining a relatively constant pH.
D) 1.0 M NH4Cl(aq) + 0.4 M HCl(aq)
NH4Cl is a salt, not a weak acid or weak base. HCl is a strong acid. Therefore, this solution does not contain a weak acid or weak base-conjugate acid pair. Hence, it is not a buffer.
E) 1.0 M NH3(aq) + 1.0 M HCl(aq)
NH3 is a weak base, and HCl is a strong acid. Since both a weak base (NH3) and its conjugate acid (NH4+) are present, this solution can act as a buffer. NH3 will react with HCl to form NH4+ and Cl-, maintaining a relatively constant pH.
Based on this analysis, the mixed solutions that are buffers are options C) 1.0 M NH3(aq) + 0.4 M HCl(aq) and option E) 1.0 M NH3(aq) + 1.0 M HCl(aq).
To determine which one of the mixed solutions is a buffer, we need to understand what constitutes a buffer solution.
A buffer solution is a solution that resists changes in pH when small amounts of acid or base are added to it. It consists of a weak acid and its conjugate base or a weak base and its conjugate acid.
To start solving this problem, we need to identify which of the given mixtures contain a weak acid and its conjugate base or a weak base and its conjugate acid.
Here's what we need to do:
1. Examine each given mixture and identify the compounds present in the solution.
2. Determine whether the compounds present in the solution can act as a weak acid and its conjugate base or a weak base and its conjugate acid.
3. Look for solutions that have an appropriate combination of weak acid/conjugate base or weak base/conjugate acid pair.
Now let's go through each option and analyze them:
A) 1.0 M NH3(aq) + 0.6 M KOH(aq)
NH3 is a weak base, but KOH is a strong base, so this mixture does not have a weak acid and its conjugate base pair. It is not a buffer solution.
B) 1.0 M NH4Cl(aq) + 1.0 M KOH(aq)
NH4Cl is a salt, and KOH is a strong base. This mixture also does not have a weak acid and its conjugate base pair. It is not a buffer solution.
C) 1.0 M NH3(aq) + 0.4 M HCl(aq)
NH3 is a weak base, and HCl is a strong acid. This mixture has a weak base (NH3) and its conjugate acid (NH4+). It is a potential buffer solution.
D) 1.0 M NH4Cl(aq) + 0.4 M HCl(aq)
NH4Cl is a salt, and HCl is a strong acid. This mixture does not have a weak acid and its conjugate base pair. It is not a buffer solution.
E) 1.0 M NH3(aq) + 1.0 M HCl(aq)
NH3 is a weak base, and HCl is a strong acid. This mixture has a weak base (NH3) and a strong acid (HCl), but it does not have the conjugate acid of the weak base. It is not a buffer solution.
From the analysis above, we can see that option C (1.0 M NH3(aq) + 0.4 M HCl(aq)) is the mixture that contains a weak base (NH3) and its conjugate acid (NH4+). Thus, option C is the buffer solution.
Therefore, the mixed solution that is a buffer is option C) 1.0 M NH3(aq) + 0.4 M HCl(aq).