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Essential Math and Calculations for Pharmacy Technicians

Indra K. Reddy, Mansoor A. Khan

Chapter 10

Working with pH and Buffers - all with Video Answers

Educators

Chapter Questions

03:01

Problem 1

What is the $\mathrm{pH}$ of a buffer solution containing $0.005 \mathrm{M}$ oxalic acid and $0.05 \mathrm{M}$ potassium oxalate solution in one-liter? The dissociation constant of oxalic acid is $6.5 \times 10^{-2}$ at $25^{\circ} \mathrm{C}$.

Ahmed Ali
Ahmed Ali
Numerade Educator
01:09

Problem 1

What is the $\mathrm{pH}$ of a liter buffer solution containing $0.5 \mathrm{M}$ boric acid and 0.25 sodium borate per liter? The $\mathrm{pK}_{\mathrm{a}}$ of boric acid is 9.24 at $25^{\circ} \mathrm{C}$.

David Collins
David Collins
Numerade Educator
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Problem 1

What is the $\mathrm{pH}$ of a buffer solution containing $0.04 \mathrm{M}$ sodium maleate solution and $0.8 \mathrm{M}$ maleic acid solution in one-liter, assuming that the dissociation constant of maleic acid is $5.5 \times 10^{-7}$ at $25^{\circ} \mathrm{C}$ ?

Ronald Prasad
Ronald Prasad
Numerade Educator
00:31

Problem 2

What is the $\mathrm{pH}$ of a buffer solution containing $0.08 \mathrm{M}$ formic acid solution and $0.2 \mathrm{M}$ sodium formate solution in one-liter, assuming that the $\mathrm{pK}_{\mathrm{a}}$ of formic acid is 3.75 at $25^{\circ} \mathrm{C}$ ?

David Collins
David Collins
Numerade Educator
01:24

Problem 3

What is the $\mathrm{pH}$ of a buffer solution containing $0.2 \mathrm{M}$ ammonium hydroxide solution and $0.04 \mathrm{M}$ ammonium chloride solution in one-liter, using the $\mathrm{Ka}$ of ammonia as $5.75 \times 10^{-10}$ at $25^{\circ} \mathrm{C}$ ?

Adriano Chikande
Adriano Chikande
Numerade Educator
01:44

Problem 4

What is the $\mathrm{pH}$ of a solution containing $0.05 \mathrm{M}$ atropine sulfate solution and $0.5 \mathrm{M}$ atropine solution in one-liter, using the $\mathrm{K}_{\mathrm{b}}$ of atropine as $4.47 \times$ $10^{-5}$ at $15^{\circ} \mathrm{C}$ ?

Henry He
Henry He
Numerade Educator
12:14

Problem 5

What is the $\mathrm{pH}$ of a solution containing $0.8 \mathrm{M}$ morphine and $0.025 \mathrm{M}$ morphine sulfate solution in one-liter, using the $\mathrm{pK}_{\mathrm{a}}$ of morphine as 7.87 at $25^{\circ} \mathrm{C}$ ?

Emmalou Schmittzehe
Emmalou Schmittzehe
Numerade Educator
01:44

Problem 6

What is the $\mathrm{pH}$ of a solution containing $0.65 \mathrm{M}$ pilocarpine solution and $0.65 \mathrm{M}$ pilocarpine sulfate solution in one-liter, using the $\mathrm{K}_{\mathrm{b}}$ of pilocarpine as $7.0 \times 10^{-8}$ at $25^{\circ} \mathrm{C}$ ?

Henry He
Henry He
Numerade Educator
03:17

Problem 7

What is the $\mathrm{pH}$ of a solution containing $0.09 \mathrm{M}$ pseudotropine solution and $0.3 \mathrm{M}$ pseudotropine sulfate solution in one-liter, using the $\mathrm{K}_{\mathrm{a}}$ of pseudotropine is $6.2 \times 10^{-11}$ at $25^{\circ} \mathrm{C}$ ?

Ronald Prasad
Ronald Prasad
Numerade Educator
02:32

Problem 9

What is the molar ratio of salt/acid needed to prepare citric acid buffer having the $\mathrm{pH} 2.8$, using a $\mathrm{pK}_{\mathrm{a}}$ of citric acid as 3.15 at $25^{\circ} \mathrm{C}$ ?

Aswathy M
Aswathy M
Numerade Educator
02:32

Problem 10

What is the molar ratio of salt/acid needed to prepare oxalic acid buffer having the $\mathrm{pH} 5.8$, using a $\mathrm{pK}_{\mathrm{a}}$ of oxalic acid of 1.19 at $25^{\circ} \mathrm{C}$ ?

Aswathy M
Aswathy M
Numerade Educator
01:27

Problem 11

What is the $\mathrm{pH}$ of a liter buffer solution containing $0.6 \mathrm{M}$ sodium acetate and $0.15 \mathrm{M}$ acetic acid? The $\mathrm{pk}_{\mathrm{a}}$ for acetic acid equals 4.76 at $25^{\circ} \mathrm{C}$.

Lucy Chang
Lucy Chang
Numerade Educator
01:27

Problem 12

What is the $\mathrm{pH}$ of a liter buffer solution containing $0.2 \mathrm{M}$ acetic acid and $0.7 \mathrm{M}$ potassium acetate? The $\mathrm{K}_{\mathrm{a}}$ of acetic acid equals $1.75 \times 10^{-5}$ at $25^{\circ} \mathrm{C}$.

Lucy Chang
Lucy Chang
Numerade Educator
02:37

Problem 13

What is $\mathrm{pH}$ of a liter buffer solution containing $0.4 \mathrm{M}$ benzoic acid and $0.045 M$ sodium benzoate? The $\mathrm{pK}_{\mathrm{a}}$ for benzoic acid equals 4.2 at $25^{\circ} \mathrm{C}$.

David Collins
David Collins
Numerade Educator
00:39

Problem 14

What is $\mathrm{pH}$ of a liter buffer solution containing $0.6 \mathrm{M}$ benzoic acid and $0.07 M$ sodium benzoate? The dissociation constant $\left(\mathrm{K}_{\mathrm{a}}\right)$ for benzoic acid at $25^{\circ} \mathrm{C}$ is $6.3 \times 10^{-5}$.

Amy Jiang
Amy Jiang
Numerade Educator
01:09

Problem 16

What is the $\mathrm{pH}$ of a liter buffer solution containing $0.7 \mathrm{M}$ boric acid and $0.5 \mathrm{M}$ sodium borate? The dissociation constant for boric acid is $5.8 \times$ $10^{-10}$ at $25^{\circ} \mathrm{C}$.

David Collins
David Collins
Numerade Educator
19:46

Problem 17

What is the $\mathrm{pH}$ of a liter citrate buffer solution containing $0.3 \mathrm{M}$ citric acid and $0.2 \mathrm{M}$ potassium citrate? The dissociation constant of citric acid is $4.0 \times 10^{-6}$ at $25^{\circ} \mathrm{C}$.

Shubham Kumar
Shubham Kumar
Numerade Educator
01:52

Problem 19

What is the $\mathrm{pH}$ of a buffer solution containing $0.06 \mathrm{M}$ oxalic acid solution and $0.4 M$ sodium oxalate solution in one-liter, assuming the dissociation constant of oxalic acid is $6.5 \times 10^{-2}$.

David Collins
David Collins
Numerade Educator
01:52

Problem 20

What is the $\mathrm{pH}$ of a buffer solution containing $2 \mathrm{M}$ potassium oxalate solution and $0.02 \mathrm{M}$ oxalic solution in one-liter, assuming the $\mathrm{pK}_{\mathrm{a}}$ of oxalic acid is 4.21 at $25^{\circ} \mathrm{C}$ ?

David Collins
David Collins
Numerade Educator
01:23

Problem 21

What is the molar ratio of base/salt required to prepare a buffer of ammonium hydroxide and ammonium chloride having the $\mathrm{pH} 7.8$, using a $\mathrm{pK}_{\mathrm{b}}$ of ammonium as 4.76 at $25^{\circ} \mathrm{C}$ ?

Adriano Chikande
Adriano Chikande
Numerade Educator
01:44

Problem 22

What percentage of atropine base exists as unionized (base form) in ophthalmic drops buffered at $\mathrm{pH} 6.8$, using a $\mathrm{pK}_{\mathrm{b}}$ of atropine of 4.35 at $25^{\circ} \mathrm{C}$ ?

Henry He
Henry He
Numerade Educator
05:18

Problem 23

What percentage of codeine base remains unionized in cough sedative syrup buffered at $\mathrm{pH} 7.0$, using a $\mathrm{pK}_{\mathrm{a}}$ of codeine of 7.95 at $25^{\circ} \mathrm{C}$ ?

Sima Sarker
Sima Sarker
Numerade Educator
04:26

Problem 24

What is the molar ratio of base/salt in colchicine base solution buffered to $\mathrm{pH} 1.8$, using a $\mathrm{K}_{\mathrm{a}}$ of colchicine of $2.23 \times 10^{-2}$ at $25^{\circ} \mathrm{C}$ ?

Ahmed Ali
Ahmed Ali
Numerade Educator
01:23

Problem 25

What is the molar ratio of salt/base required to adjust the $\mathrm{pH}$ to 8.5 using ammonium hydroxide-ammonium chloride buffer, using $\mathrm{K}_{\mathrm{b}}$ of ammonium hydroxide of $1.77 \times 10^{-5}$ at $25^{\circ} \mathrm{C}$ ?

Adriano Chikande
Adriano Chikande
Numerade Educator
05:18

Problem 26

What percentage of codeine base is expected to exist in the unionized form in cough sedative syrup buffered at $\mathrm{pH} 6.5$, using a $\mathrm{pK}_{\mathrm{a}}$ of codeine of 7.95 at $25^{\circ} \mathrm{C}$ ?

Sima Sarker
Sima Sarker
Numerade Educator
01:27

Problem 27

What is the $\mathrm{pH}$ of a buffer solution containing $0.095 \mathrm{M}$ acetic acid and $0.6 \mathrm{M}$ sodium acetate? The dissociation constant of acetic acid is $1.75 \times$ $10^{-5}$ at $25^{\circ} \mathrm{C}$.

Lucy Chang
Lucy Chang
Numerade Educator
03:47

Problem 28

What is the molar ratio of salt/base required to prepare a buffer of ephedrine and ephedrine hydrochloride having $\mathrm{pH}$ 8.8? The $\mathrm{pK}_{\mathrm{a}}$ of ephedrine is 9.36 at $25^{\circ} \mathrm{C}$.

Ronald Prasad
Ronald Prasad
Numerade Educator
00:51

Problem 29

What is the molar ratio of boric acid/sodium borate required to prepare boric acid ophthalmic solution of $\mathrm{pH} 6.5$ ? The $\mathrm{pK}_{\mathrm{a}}$ of boric acid is 9.24.

David Collins
David Collins
Numerade Educator
01:23

Problem 30

What is the molar ratio of ammonium chloride/ammonium hydroxide required to prepare ammonia buffer of $\mathrm{pH} 9.25$ ? The $\mathrm{Kb}$ of ammonium hydroxide is $1.8 \times 10^{-5}$ at $25^{\circ} \mathrm{C}$.

Adriano Chikande
Adriano Chikande
Numerade Educator
00:35

Problem 78

What is the molar ratio of salt/acid needed to prepare a citric acid buffer having the $\mathrm{pH} 5.2$ ? The $\mathrm{pK}_{\mathrm{a}}$ of citric acid is 4.78 at $25^{\circ} \mathrm{C}$ ?

Hunza Gilgit
Hunza Gilgit
Numerade Educator