RX 351 – Basic Pharmaceutics
Nandita G. Das, Ph.D., R.Ph.
Page 1 of 4
M2.B3 Practice Challenge Level Problems with % w/w
Applications
The following problem set is for your practice and self-assessment. You may use any resource
you wish to in order to work the problems.This assignment will not be graded, and is designed
for self-directed learning. Completion of the assignment is not mandatory, and your progress
will not be monitored. There are no points associated with this assignment. The solutions are
provided – you may compare your answers against the given solution sheet to check your work
and identify areas where you need more work and/or help from your instructors or peers. The
instructor is available to answer any questions you may have, either by e-mail, during the live
synchronous sessions, or meetings set up via Zoom.
1. How many grams of sorbitol powder will be required to prepare a 20% w/w sorbitol
solution using 100 mL of water as solvent? Molecular weight of sorbitol = 182.17 g/mol;
Density of sorbitol = 1.49 g/mL
2. Prepare 500 mL of 5% w/w sucrose syrup (default vehicle for syrup = water). Perform
calculations, and write a brief procedure as if you were executing this task in the
laboratory.
RX 351 – Basic Pharmaceutics
Nandita G. Das, Ph.D., R.Ph.
Page 2 of 4
3. One kilogram of sucrose was added to one liter of water to prepare a syrup. What is the
%w/w strength of the syrup?
A) 0.1 % w/w
B) 1 % w/w
C) 10 % w/w
D) 50 % w/w
E) 100% w/w
4. Consider the following formula:
Sorbitol 10 % w/v
Water qs ad 100 mL
How many milliliters of commercially available Sorbitol Solution USP (70% w/w, SG 1.28 at
25°C) will be required to compound the Rx?
RX 351 – Basic Pharmaceutics
Nandita G. Das, Ph.D., R.Ph.
Page 3 of 4
5. Given the information that the specific gravity of glycerin is 1.25 at 25°C, you will need
to add _______ g calamine powder to 100 mL glycerin to prepare a 20% w/w calamine
lotion.
6. What is the % w/v strength of the calamine lotion in the previous problem? Density of
calamine powder is 5.610 g/cm3.
7. A 4.00 gram sample of NaOH (solid) is dissolved in enough water to make 0.50 liter of
solution. What is the normality of this solution? FW of NaOH = 40 g/mol
RX 351 – Basic Pharmaceutics
Nandita G. Das, Ph.D., R.Ph.
Page 4 of 4
8. A solution of hydrochloric acid has a density of 1.15 grams per milliliter and is 30% by
mass HCl.
(a) What is the molarity of this solution of HCl?
(b) What volume of this solution should be taken in order to prepare 5 liters of 0.2 M
hydrochloric acid by dilution with water?