Which of the following pairs would make a good buffer solution in an aqueous solution?

A) H2SO4 and NaHSO4
B) Ca(NO3)2 and HNO3
C) HCl and NaCl
D) HF and NaOH
E) none of them

I know the answer is D but I don't understand why. I would think it would be C since a goo buffer is a weak acid and it's salt.

You are right. D is the correct answer. You are also correct that a good buffer is a weak acid or weak base and its conjugate base/acid. However, HCl is not a weak acid; therefore, it along with sodium chloride is not a good buffer. D is a good buffer because it is a weak acid and its salt. A is not a good buffer because sulfuric acid is not a weak acid. B is not a good buffer because nitric acid is not a weak acid. C is not a good buffer for reasons already outlined.

Ah, the wonderful world of chemistry. Let's tackle this together, my friend. When it comes to buffer solutions, we want a weak acid and its conjugate base (or a weak base and its conjugate acid). These pairs work together to resist changes in pH.

Now, in option C, we have HCl, which is indeed a strong acid, but its conjugate base, NaCl, is not really a weak base. So, it wouldn't make a good buffer solution.

But in option D, we have HF, which is a weak acid, and NaOH, which is a strong base. When these two are mixed together, they form the weak base NaF, which makes this pair a good buffer solution.

So, you got it right! Option D is the winner. Keep up the good work, and remember that chemistry is all about finding that perfect balance, just like a good joke!

The correct answer is D) HF and NaOH. Let's understand why D is correct and why the other options are not suitable as buffer solutions.

A buffer solution is a solution that can resist changes in pH when a small amount of an acid or base is added to it. To act as a buffer, a solution should contain a weak acid and its conjugate base, or a weak base and its conjugate acid.

Let's analyze the options given:

A) H2SO4 and NaHSO4 - This pair consists of a strong acid (H2SO4) and its salt (NaHSO4). Both species will ionize completely in water, indicating that this is not a suitable buffer solution.

B) Ca(NO3)2 and HNO3 - This pair consists of a strong acid (HNO3) and its salt (Ca(NO3)2). Similar to option A, this is not a suitable buffer solution as both species will ionize completely in water.

C) HCl and NaCl - This pair consists of a strong acid (HCl) and its salt (NaCl). Again, both species will ionize completely in water, making this unsuitable for a buffer solution.

D) HF and NaOH - This pair consists of a weak acid (HF) and a strong base (NaOH). HF will partially ionize in water, creating a mixture of its ions (F- and H+). NaOH is a strong base that will ionize completely, producing Na+ and OH- ions. The presence of both the weak acid (HF) and its conjugate base (F-) makes this a suitable buffer solution.

E) none of them - This option implies that none of the pairs is suitable for a buffer solution, but as discussed above, option D is indeed a suitable buffer solution.

Therefore, the correct answer is D) HF and NaOH, as it contains a weak acid (HF) and a strong base (NaOH) necessary for a buffer solution.

To determine which of the given pairs would make a good buffer solution, we need to understand the characteristics of 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.

Let's examine each of the given options:

A) H2SO4 and NaHSO4: H2SO4 is a strong acid, not a weak acid, so it does not make a good buffer. Additionally, NaHSO4 is the salt of a strong acid and a weak base, so it does not provide a suitable conjugate base for the weak acid.

B) Ca(NO3)2 and HNO3: Ca(NO3)2 is a salt but not a weak base, so it does not provide a suitable conjugate base for a weak acid. HNO3 is a strong acid, which also does not meet the requirements of a buffer solution.

C) HCl and NaCl: HCl is a strong acid and not a weak acid, so it does not make a good buffer. NaCl is the salt of a strong acid and a strong base, so it does not provide a suitable conjugate base for HCl.

D) HF and NaOH: HF is a weak acid, which can serve as the acid in a buffer solution. NaOH is a strong base and not suitable as a conjugate base. However, if we consider the reaction between HF and NaOH, HF can partially dissociate to provide a small amount of F- ions, which can act as the conjugate base for HF. This combination of HF and its conjugate base F- can help maintain the pH of the solution and make a good buffer.

E) None of them: As explained above, option D (HF and NaOH) makes a good buffer solution, so the correct answer is not "None of them."

Therefore, the correct answer is D) HF and NaOH.