Question

You have the following reagents on hand:

Solids (pKa of acid form is given)	Solutions
Benzoic acid (4.19)	5 M HCl
Sodium acetate (4.74)	1 M acetic acid (4.74)
Potassium fluoride (3.14)	2.6 M NaOH
Ammonium chloride (9.26)	2.6 M NaOH

What combinations of reagents would you use to prepare buffers at the following pH values?

a.3 b.4 c.5 d.7 e.9

Short answer

Thecombination of reagents I would use to prepare buffer at this pHare listed below:

a) Potassium fluoride andHCl;

b) Benzoic acid andNaOH

c) Sodium acetate and acetic acid

d) HOClandNaOH or ammonium chloride andsodium acetate

e) Ammonium chloride andNaOH.

Step-by-step solution

Use reagents to prepare buffer at pH 3

The equal quantities presence and its conjugate base have been shown by the buffer. The ratiofor a buffer solution is equal to 1 approximately. The relationship between pH and pK_ais denoted by Henderson Hasselbalch equation.

$pH=p{K}_a+\log \frac{\left[salt\right]}{\left[acid\right]}$

The given pH is 3. HCl and potassium fluoride areneeded. The preparation of buffer by HCl+KF works together inthe pH range of 2.14 to 4.14.

Usereagents to prepare buffer at pH 4

The equal quantities presence and its conjugate base have been shown by the buffer. The ratio for a buffer solution is equal to 1 approximately. The relationship between pH and pK_ais denoted by the Henderson Hasselbalch equation.

$pH=p{K}_a+\log \frac{\left[salt\right]}{\left[acid\right]}$

The given pH is 4. Sodium acetate and acetic acid areneeded. The pH of acetic acid is 4.72. The preparedbuffer works efficientlywithin the pH range of 3.72 to 4.72. NaOH and Benzoic acid are used to prepare abuffer of benzoate and benzoic acid.

Usereagents to prepare buffer at pH 5

The equal quantities presence and its conjugate base have been shown by the buffer. The ration for a buffer solution is equal to 1 approximately. The relationship between pH and pK_ais denoted by the Henderson Hasselbalch equation.

$pH=p{K}_a+\log \frac{\left[salt\right]}{\left[acid\right]}$

The given pH is 5. Sodium acetate and acetic acid areneeded. The preparation of buffer by acetic acid and sodium acetate works together in thepH range of 3.72 to 4.72.

 Step 4: Usereagents to prepare buffer at pH 7

The equal quantities presence and its conjugate base have been shown by the buffer. The ration for a buffer solution is equal to 1 approximately. The relationship between pH and pK_ais denoted by the Henderson Hasselbalch equation.

$pH=p{K}_a+\log \frac{\left[salt\right]}{\left[acid\right]}$

The given pH is 7. NaOH and HOClareneeded. The buffer works efficiently in the pH range of 6.46 to 8.46.

Usereagents to prepare buffer at pH 9

The equal quantities presence and its conjugate base have been shown by the buffer. The ration for a buffer solution is equal to 1 approximately. The relationship between pH and pK_ais denoted by the Henderson Hasselbalch equation.

$pH=p{K}_a+\log \frac{\left[salt\right]}{\left[acid\right]}$

The given pH is 9. NaOH and ammonium chlorideareneeded. The buffer works efficiently in the pH range of8.26 to 10.26. NaOH and NH₄Cl can be used to make a buffer of NH₄⁺ and NH₃.