Practice Questions Liquids Monophasic Liquids PDF

##### **[Review Questions]** 1\. Solution dosage forms are officially described as: 2\. Why does dissolution cease when the concentration of solute in the bulk solution is equivalent to the solubility of the solute? 3\. Which of the following would likely increase the solubility of an endothermic...

##### **[Review Questions]** 1\. Solution dosage forms are officially described as: 2\. Why does dissolution cease when the concentration of solute in the bulk solution is equivalent to the solubility of the solute? 3\. Which of the following would likely increase the solubility of an endothermic, polar solute? 4\. A pharmacist is preparing to compound 60 mL of a 5% (*w/v*) drug solution using water as the solvent. Based upon the drug having a solubility of 1 g / 3.6 mL water, will the pharmacist be able to prepare a solution product? *(why / why not?)* 5\. If the water solubility of an exothermic drug is 1 g/23 mL at 25^o^C, what is the minimum volume of water that will dissolve the amount of drug needed to prepare the following prescription? *Rx Drug 1% (w/v)* *Purified Water qs 60 mL* a. 14 mL b. 23 mL c. 59 mL d. 99 mL 7\. If an endothermic drug has a water solubility of 1 g / 14.2 ml at 25^o^C, what is the highest approximate solution concentration that may be prepared at that temperature? ***c. 7%*** 8\. Can 500 mg of drug be delivered in one tablespoonful of solution if the solubility of the drug in the desired solvent is 1 g / 5.6 mL? 9\. In terms of intermolecular forces, describe the difference between polar and non-polar solvents and provide one example of each: 10\. Which of the following non-bonding interactions is an example of a van der Waals force? 11\. A pharmaceutical company is attempting to prepare a solution of a new drug using a water:glycerin co-solvent system. What is the maximum concentration that may be prepared using a 75:25 mixture of water:glycerin? *(the solubility of the drug in water and glycerin is 2.5 mg/ml and 20 mg/ml, respectively)* a. 3.1 mg/mL b. 4.2 mg/mL c. 9.4 mg/mL d. 12.0 mg/mL e. None of the above 12\. A pharmacist is attempting to prepare a solution of a drug using a 50:25:25 water:glycerin:Alcohol, USP co-solvent system. If the solubility of the drug in water, glycerin, and Alcohol, USP is 5 mg/mL, 15 mg/mL, and 55 mg/mL, respectively, what is the maximum drug concentration that may be prepared using this co-solvent system? a. 5 mg/mL b. 12 mg/mL c. 55 mg/mL d. 129 mg/mL e. None of the above 13\. A pharmacist is trying to prepare a 1.5% solution of phenobarbital using a water:ethanol co-solvent system. What percentage of water and ethanol does the pharmacist need to use? *(the solubility of phenobarbital in water and ethanol is 1.4 mg/ml and 91 mg/ml, respectively)* a. If the solubility of the drug in the liquid medicine is 750 mg/ml and the solubility in the juice is 250 mg/ml, calculate the solubility of the drug in the liquid medicine:juice mixture: 15\. Calculate the dielectric constant for a mixture of 40% glycerin in H~2~O: *(ε~water~ = 80; ε~glycerin~ = 46)* **16**. Which of the following is characteristic of an exothermic drug? 17\. Describe the difference between exothermic and endothermic materials including how this difference affects the solubility of each: 18\. If the water solubility of caffeine was determined to be 0.167 g/ml at 80^o^C, what is its expected solubility at 25^o^C? *(the heat of fusion for caffeine is 21.0 kJ/mol)* a. 0.045 g/mL b. 0.146 g/mL c. 0.313 g/mL d. 0.625 g/mL 19\. If the water solubility of a new excipient was determined to be 0.25 mg/ml at 25^o^C, what is the expected solubility of the excipient at 4^o^C? *(the heat of fusion for the excipient is -13.0 kJ/mol)* a. 0.05 mg/mL b. 0.17 mg/mL c. 0.25 mg/mL d. 0.37 mg/mL e. None of the above 20\. An investigational drug substance (∆H = -38.6 kJ/mol) was found to have a water solubility of 1.05% at 25^o^C. What temperature must be used to achieve a solubility of 3.25%? 21\. If the **water solubility of a particular drug is 1 g in 7.5 ml of water at 25^o^C and the heat of fusion is 42,600 J/mol. How much water would be needed to dissolve 1 g of drug at 4^o^C?** 22\. If the **water solubility of an active ingredient was found to be 105 mg/mL at 25^o^C and 250 mg/ml at 50^o^C, calculate the heat of fusion for the active ingredient:** 23\. Which of the following statements regarding solvents is ***true***? a. Alcohol, USP has a lower dielectric constant than water b. Fixed oils are not water-miscible c. Glycerin is often used as a humectant within otic solutions d. b & c e. All of the above 24\. Which of the following may be used to mask taste by anesthetizing the taste buds? 25\. Which of the following vehicles may be described as clear, aqueous solutions saturated with volatile oils or other aromatic/volatile substances? 26\. If a new drug is prepared as a free base, which of the following tastes is it most likely to have? a. ***Bitter*** b. Salty c. Sour d\. Sweet 28\. Indicate two potential advantages of using a co-solvent system to prepare a solution dosage form: 30\. A pharmacist receives a prescription requiring 0.6 mL of an aqueous flavoring; however, the smallest measuring device available is a graduated cylinder having a capacity of 20 mL. 31\. A pharmacist receives a prescription requiring 0.2 mL of peppermint oil; however, the smallest graduated cylinder available has a capacity of 15 mL. 32\. Which of the following statements regarding weak electrolytes is ***true***? 33\. PO~4~^-3^ may act as... 34\. An acid may be defined as a proton \_\_\_\_\_\_\_\_; whereas, a base may be defined as a proton \_\_\_\_\_\_\_\_. *(indicate either "acceptor" or "donor")* 35\. Which of the following is a weak base? a. Acetic acid b. Ammonia c. Ammonium acetate d. Ammonium chloride e. 36\. Sodium phenytoin is a...? a. Weak acid b. Weak base c. Salt of a weak acid d. ***Salt of a weak base*** e. Salt of a weak acid and a weak base 37\. Which of the following is the weakest acid? 38\. Which of the following is the strongest base? a. A drug having a K~b~ of 1.74x10^-4^ b. A excipient having a pK~a~ of 4.76 c. d. e. 39\. Calculate the pH of a 0.1 M solution of potassium acetate: *(K~a~ = 1.75 x 10^-3^)* a\. 6.12 b\. 6.38 40\. Calculate the pH of a 0.5 M solution of sodium phenytoin: *(phenytoin: pK~a~ = 4.61)* a. b. c. d. e. 41\. Calculate the pH of a 0.05 M solution of atropine sulfate: *(atropine: K~b~ = 4.47x10^-5^)* **43. Calculate the pH of a 0.05 M NaOH solution:** 45\. Which of the following statements regarding buffers is ***false***? a. May potentially improve the chemical stability of solutions b. Consist of a mixture of weak acids and their conjugate bases, or weak bases and their conjugate acids c. A buffer containing 0.05 M acetic acid and 0.05 M sodium acetate will have a lower pH than one containing 0.5 M acetic acid and 0.5 M sodium acetate d. The pH:pKa ratio of a buffer influences its buffer capacity e. Used to resist changes in the pH of solution dosage forms 46\. Calculate the pH of a buffer consisting of 0.5 M acetic acid and 0.25 M sodium acetate: *(acetic acid: pK~a~ = 4.76)* a\. 4.46 b\. 5.06 a\. 0.025 M b\. 0.83 M 48\. If NaOH were added to a buffer so that the final NaOH concentration is 0.05 M and the pH of the buffer increased by 0.02 pH units, what is the capacity of the buffer? 49\. A pharmacist just prepared a 0.3 molar acetate buffer having a pH of 4.5. Calculate the hydrogen ion, acetate ion, and acetic acid concentrations: *(for acetic acid, pK~a~ = 4.76)* 50\. What is the pH of a solution of 0.05 M trimethylamine and 0.15 M trimethylamine nitrate? *(trimethylamine, pK~b~ = 4.2)* **[EQUATIONS, CONVERSIONS, ETC.]** pH = pK~a~ + log β = pH - pK~a~ = log pH - pK~a~ = log ##### ##### **[Review Questions Answer Key]** 1\. Solution dosage forms are officially described as: ***-- LO 1*** 2\. Why does dissolution cease when the concentration of solute in the bulk solution is equivalent to the solubility of the solute? ***-- LO 2*** 3\. Which of the following would likely increase the solubility of an endothermic, polar solute? ***-- LO 2*** 4\. A pharmacist is preparing to compound 60 mL of a 5% (*w/v*) drug solution using water as the solvent. Based upon the drug having a solubility of 1 g / 3.6 mL water, will the pharmacist be able to prepare a solution product? *(why / why not?) **-- LO 3*** ***3.6 ml water / 1 g drug x 3 g drug = 10.8 ml water*** 5\. If the water solubility of an exothermic drug is 1 g/23 mL at 25^o^C, what is the minimum volume of water that will dissolve the amount of drug needed to prepare the following prescription? ***-- LO 3*** *Rx Drug 1% (w/v)* *Purified Water qs 60 mL* a. ***14 mL*** b. 23 mL c. 59 mL d. 99 mL ***1 g drug / 20.3 ml water x 100 ml solution ≈ 4.9 % solution*** ***The desired drug concentration (12.5%) is greater than the highest approximate solution concentration (4.9 %) that can be prepared. Therefore, the desired solution cannot be compounded.*** ***This may also be determined by comparing the volume of water needed to dissolve the desired amount of drug to the volume of solution prescribed:*** 7\. If an endothermic drug has a water solubility of 1 g / 14.2 ml at 25^o^C, what is the highest approximate solution concentration that may be prepared at that temperature? ***-- LO 3*** ***c. 7% Note: this is an approximation since water ≠ solution*** 8\. Can 500 mg of drug be delivered in one tablespoonful of solution if the solubility of the drug in the desired solvent is 1 g / 5.6 mL? ***-- LO 3*** ***Calculate the quantity of solvent needed to dissolve the desired dose:*** ***5.6 mL solvent / 1 g drug x 1 g / 1000 mg x 500 mg drug = 2.8 mL solvent*** ***One tablespoonful = 15 mL of solution \>\> 2.8 mL of solvent, so 500 mg of drug should be able to be delivered in one tablespoonful of the solution*** 9\. In terms of intermolecular forces, describe the difference between polar and non-polar solvents and provide one example of each: ***-- LO 4*** 10\. Which of the following non-bonding interactions is an example of a van der Waals force? ***-- LO 4*** 11\. A pharmaceutical company is attempting to prepare a solution of a new drug using a water:glycerin co-solvent system. What is the maximum concentration that may be prepared using a 75:25 mixture of water:glycerin? *(the solubility of the drug in water and glycerin is 2.5 mg/ml and 20 mg/ml, respectively) **-- LO 5*** a. 3.1 mg/mL b. ***4.2 mg/mL*** c. 9.4 mg/mL d. 12.0 mg/mL 12\. A pharmacist is attempting to prepare a solution of a drug using a 50:25:25 water:glycerin:Alcohol, USP co-solvent system. If the solubility of the drug in water, glycerin, and Alcohol, USP is 5 mg/mL, 15 mg/mL, and 55 mg/mL, respectively, what is the maximum drug concentration that may be prepared using this co-solvent system? ***-- LO 5*** a. 5 mg/mL b. ***12 mg/mL*** c. 55 mg/mL d. 129 mg/mL e. None of the above 13\. A pharmacist is trying to prepare a 1.5% solution of phenobarbital using a water:ethanol co-solvent system. What percentage of water and ethanol does the pharmacist need to use? *(the solubility of phenobarbital in water and ethanol is 1.4 mg/ml and 91 mg/ml, respectively) -- LO 5* ***1.5 g drug / 100 ml solution x 1000 mg / 1 g = 15 mg / ml*** *log 15 = \[log 1.4\](f~water~) + \[log 91\](1 - f~water~)* *1.18 = 0.146(f~water~) + 1.96 -- 1.96(f~water~)* *-0.78 = -1.8(f~water~)* *0.43 = f~water~ f~ethanol~ = 1 - f~water~ = 1 -- 0.43 = 0.57* *At least a 43:57 water:ethanol ratio is needed; however, any ratio having less water and more alcohol would also ensure enough solubility to prepare the desired concentration* a. If the solubility of the drug in the liquid medicine is 750 mg/ml and the solubility in the juice is 250 mg/ml, calculate the solubility of the drug in the liquid medicine:juice mixture: ***-- LO 5*** *log Ks^T^ = \[log 750\](0.33) + \[log 250\](0.66)* *log Ks^T^ = 2.53* *Ks^T^ = 339 mg/ml* 15\. Calculate the dielectric constant for a mixture of 40% glycerin in H~2~O: *(ε~water~ = 80; ε~glycerin~ = 46) -- LO 5* *ε~T~ = 80(0.6) + 46(0.4)* *ε~T~ = 66.4* **16**. Which of the following is characteristic of an exothermic drug? ***-- LO 6*** 17\. Describe the difference between exothermic and endothermic materials including how this difference affects the solubility of each: ***-- LO 6*** 18\. If the water solubility of caffeine was determined to be 0.167 g/ml at 80^o^C, what is its expected solubility at 25^o^C? *(the heat of fusion for caffeine is 21.0 kJ/mol) -- LO 7* a. ***0.045 g/mL*** b. 0.146 g/mL c. 0.313 g/mL d. 0.625 g/mL 19\. If the water solubility of a new excipient was determined to be 0.25 mg/ml at 25^o^C, what is the expected solubility of the excipient at 4^o^C? *(the heat of fusion for the excipient is -13.0 kJ/mol) -- LO 7* a. 0.05 mg/mL b. 0.17 mg/mL c. 0.25 mg/mL d. ***0.37 mg/mL*** e. None of the above 20\. An investigational drug substance (∆H = -38.6 kJ/mol) was found to have a water solubility of 1.05% at 25^o^C. What temperature must be used to achieve a solubility of 3.25%? *-- LO 7* 21\. If the **water solubility of a particular drug is 1 g in 7.5 ml of water at 25^o^C and the heat of fusion is 42,600 J/mol. How much water would be needed to dissolve 1 g of drug at 4^o^C? *-- LO 7*** ***1 g / 7.5 mL = 0.133 g / mL*** ***ln (Ks^2^ / Ks^1^) = (∆H / R)\*((T~2~ -- T~1~)/(T~2~T~1~))*** ***ln (Ks^2^ / 0.133) = (42,600 J/mol / 8.3145 J/mol-K)\*((277K -- 298 K)/(277 K\*298 K))*** ***ln (Ks^2^ / 0.133) = -1.3*** ***Ks^2^ / 0.133 = 0.273*** ***Ks^2^ = 0.036 g / mL 1 mL / 0.036 g x 1 g = 27.8 mL*** ***The heat of fusion is (+) and therefore the solubility decreases with a decrease in temperature. As a result, more water is needed (27.8 mL vs. 7.5 mL) to dissolve the same amount of drug*** 22\. If the **water solubility of an active ingredient was found to be 105 mg/mL at 25^o^C and 250 mg/ml at 50^o^C, calculate the heat of fusion for the active ingredient: *-- LO 7*** ***ln (Ks^2^ / Ks^1^) = (∆H / R)\*((T~2~ -- T~1~)/(T~2~T~1~))*** ***ln (105 / 250) = (∆H / 8.3145 J/mol-K)\*((298K -- 323 K)/(298 K\*323 K))*** ***-0.868 = (∆H)\*(-3.12x10^-5^)*** ***∆H = 27,787 J/mol*** ***Note that the heat of fusion is positive, which we would expect for a material whose solubility increases with an increase in temperature*** 23\. Which of the following statements regarding solvents is ***true***? ***-- LO 8*** a. Alcohol, USP has a lower dielectric constant than water ***(Alcohol, USP is less polar than water giving it a lower dielectric constant)*** b. Fixed oils are not water-miscible c. Glycerin is often used as a humectant within otic solutions d. b & c e. ***All of the above*** 24\. Which of the following may be used to mask taste by anesthetizing the taste buds? ***-- LO 8*** 25\. Which of the following vehicles may be described as clear, aqueous solutions saturated with volatile oils or other aromatic/volatile substances? ***-- LO 9*** 26\. If a new drug is prepared as a free base, which of the following tastes is it most likely to have? ***-- LO 10*** a. ***Bitter*** b. Salty c. Sour 28\. Indicate two potential advantages of using a co-solvent system to prepare a solution dosage form: ***-- LO 11*** 30\. A pharmacist receives a prescription requiring 0.6 mL of an aqueous flavoring; however, the smallest measuring device available is a graduated cylinder having a capacity of 20 mL. ***-- LO 12*** ***4 mL / 0.6 mL = 6.67 7 (aliquot number)*** ***0.6 mL x 7 = 4.2 mL flavoring*** ***4.2 mL x 7 = 29.4 mL dilution (4.2 mL flavoring qs'ed to 29.4 mL with solvent)*** ***29.4 mL / 7 = 4.2 mL aliquot of dilution contains 0.6 mL of flavoring*** 31\. A pharmacist receives a prescription requiring 0.2 mL of peppermint oil; however, the smallest graduated cylinder available has a capacity of 15 mL. ***-- LO 12*** ***3 mL / 0.2 mL = 15*** ***0.2 mL x 15 = 3 mL peppermint oil*** ***3 mL x 15 = 45 mL dilution*** ***45 mL / 15 = 3 mL of dilution containing 0.2 mL of peppermint oil*** 32\. Which of the following statements regarding weak electrolytes is ***true***? ***-- LO 17*** 33\. PO~4~^-3^ may act as... ***-- LO 18*** 34\. An acid may be defined as a proton ***[donor]***; whereas, a base may be defined as a proton ***[acceptor]***. *(indicate either "acceptor" or "donor")* ***-- LO 18*** 35\. Which of the following is a weak base? ***-- LO 20*** a. Acetic acid b. ***Ammonia*** c. Ammonium acetate d. Ammonium chloride ***(chloride indicates that it is a salt, in particular one created from a strong acid such as HCl, further indicating that ammonia is a weak base)*** e. 36\. Sodium phenytoin is a...? ***-- LO 20*** a. Weak acid b. Weak base c. ***Salt of a weak acid (sodium indicates that it is a salt, in particular one created from a strong base such as NaOH, further indicating that phenytoin is likely a weak acid)*** d. ***Salt of a weak base*** e. Salt of a weak acid and a weak base 37\. Which of the following is the weakest acid? ***-- LO 21*** 38\. Which of the following is the strongest base? ***-- LO 21*** a. ***A drug having a K~b~ of 1.74x10^-4^*** b. A excipient having a pK~a~ of 4.76 ***(pK~b~ = 9.24 K~b~ of 5.75x10^-10^)*** c. d. e. 39\. Calculate the pH of a 0.1 M solution of potassium acetate: *(K~a~ = 1.75 x 10^-3^)* ***-- LO 22*** a\. 6.12 b\. 6.38 40\. Calculate the pH of a 0.5 M solution of sodium phenytoin: *(phenytoin: pK~a~ = 4.61)* ***-- LO 22*** a. 2.46 b. 4.86 c. ***9.15*** d. 11.5 e. None of the above 41\. Calculate the pH of a 0.05 M solution of atropine sulfate: *(atropine: K~b~ = 4.47x10^-5^)* ***-- LO 22*** **43. Calculate the pH of a 0.05 M NaOH solution: *-- LO 22*** ***pOH = -log\[OH^-^\] = -log\[C~b~\] = -log\[0.05\] = 1.30*** ***pH = pKw -- pOH = 14.0 - 1.30 = 12.7 (basic pH)*** 45\. Which of the following statements regarding buffers is ***false***? ***-- LO 25*** a. May potentially improve the chemical stability of solutions b. Consist of a mixture of weak acids and their conjugate bases, or weak bases and their conjugate acids c. ***A buffer containing 0.05 M acetic acid and 0.05 M sodium acetate will have ~~a lower~~ the same pH ~~than~~ as one containing 0.5 M acetic acid and 0.5 M sodium acetate (pH depends upon the ratio of the components, not their concentration)*** d. The pH:pKa ratio of a buffer influences its buffer capacity e. Used to resist changes in the pH of solution dosage forms 46\. Calculate the pH of a buffer consisting of 0.5 M acetic acid and 0.25 M sodium acetate: *(acetic acid: pK~a~ = 4.76)* ***-- LO 26*** ***a. 4.46*** b\. 5.06 a\. 0.025 M ***b. 0.83 M*** 48\. If NaOH were added to a buffer so that the final NaOH concentration is 0.05 M and the pH of the buffer increased by 0.02 pH units, what is the capacity of the buffer? ***-- LO 26*** 49\. A pharmacist just prepared a 0.3 molar acetate buffer having a pH of 4.5. Calculate the hydrogen ion, acetate ion, and acetic acid concentrations: *(for acetic acid, pK~a~ = 4.76) **-- LO 26*** ***\[H^+^\] = 3.16x10^-5^ M*** ***[Acetic acid concentration]:*** ***pH = pKa + log*** ***4.5 = 4.76 + log*** ***= 0.55; we also know \[acetic acid\] + \[acetate\] = 0.3 M*** ***\[acetic acid\] + \[(acetic acid)\*(0.55)\] = 0.3 M*** ***1.55\[acetic acid\] = 0.3M*** ***\[acetic acid\] = 0.194 M*** ***\[acetate\] = 0.106 M*** 50\. What is the pH of a solution of 0.05 M trimethylamine and 0.15 M trimethylamine nitrate? *(trimethylamine, pK~b~ = 4.2) **-- LO 26*** ***pH = 9.8 + log = 9.8 -- 0.477 = 9.32***