Which of the following solution should be mixed with 50.0 mL of 0.050 M HF solution to make an effective buffer?
A) 50.0 mL of 0.10 M NaOH
B) 25.0 mL of 0.10 M NaOH
C) 50.0 mL of 0.050 M NaOH
D) 25.0 mL of 0.050 M NaOH
SIR PLEASE EXPLAIN THE ANSWER
To create an effective buffer solution, we need to mix a weak acid (HF) with its conjugate base (NaF). The concentration of the acid and its conjugate base should be roughly equal.
Given:
Initial volume of HF solution (acid) = 50.0 mL
Concentration of HF solution (acid) = 0.050 M
Now let's analyze each option to see which one is suitable.
A) 50.0 mL of 0.10 M NaOH:
This is not a suitable option because NaOH is a strong base and will completely neutralize the HF, resulting in the formation of water and sodium fluoride (NaF).
B) 25.0 mL of 0.10 M NaOH:
This option is also not suitable because it would result in an excess of the strong base NaOH when mixed with HF.
C) 50.0 mL of 0.050 M NaOH:
This option appears suitable because it matches the concentration of the HF solution. However, NaOH is a strong base, so it would still neutralize most of the HF and may not create an effective buffer.
D) 25.0 mL of 0.050 M NaOH:
This option is the best choice because it allows for a roughly equal concentration of HF and NaF. This will result in the formation of a buffer solution.
Therefore, the correct option is D) 25.0 mL of 0.050 M NaOH.
To determine which solution should be mixed with the 50.0 mL of 0.050 M HF solution to make an effective buffer, we need to understand the concept of a buffer.
A buffer is a solution that can resist changes in pH when small amounts of acid or base are added to it. Buffers are typically made by combining a weak acid (or its conjugate base) with a salt of the acid (or its conjugate base).
In this case, HF is a weak acid, and we need to find a solution to mix with it to create a buffer.
To make an effective buffer, we need to mix a weak acid with its conjugate base (or a weak base with its conjugate acid) in roughly equal concentrations. This means we need to find a solution of a weak base that matches the concentration of our weak acid solution.
By looking at the given options:
A) 50.0 mL of 0.10 M NaOH
B) 25.0 mL of 0.10 M NaOH
C) 50.0 mL of 0.050 M NaOH
D) 25.0 mL of 0.050 M NaOH
We can see that options A and B have a higher concentration of NaOH compared to the concentration of HF, which means they are not in equal concentrations and will not create an effective buffer.
Options C and D have the same concentration of NaOH (0.050 M) as HF, but the volume differs. To determine which one is the correct choice, we need to calculate the total moles of acid (HF) and base (NaOH) in each option.
For option C:
Total moles of HF = (0.050 M) * (0.050 L) = 0.0025 moles
Total moles of NaOH = (0.050 M) * (0.050 L) = 0.0025 moles
For option D:
Total moles of HF = (0.050 M) * (0.050 L) = 0.0025 moles
Total moles of NaOH = (0.050 M) * (0.025 L) = 0.00125 moles
From the calculations, we can see that option C has the same number of moles of both HF and NaOH, making it the appropriate solution to mix with the 50.0 mL of 0.050 M HF solution to create an effective buffer.
Therefore, the correct option is C) 50.0 mL of 0.050 M NaOH.
An effective buffer for WHAT?
Buffers are weak acids and salt of the weak acid (or weak base and salt of the weak base). You have 50 x 0.05 = 2.5 millimoles HF which is the weak acid. If you mix NaOH with that you will produce NaF which is the salt. However, you can't add TOO much NaOH else you have no acid left. Look at each of the following and pick one that leaves some of the acid while it is making some of the salt. I'll give you a hint: the answer is not C.
A is 50 x 0.1M = 5 mmols NaOH
B is 25 x 0.1M = 2.5 mmols NaOH
C is 50 x 0.05M = 2.5 mmols NaOH
D is 25 x 0.05M = 1.25 mmols NaOH
.........HF + NaOH ==> NaF + H2O
A.......2.5...5.........x.....x
B.......2.5...2.5.......x.....x
C.......2.5...2.5.......x.....x
D.......2.5...1.25......x.....x