Practice problems

# Question
1 How many milliliters of water should be added to 230 ml of a 32 % (w/v) solution to prepare 9 % w/v solution?
2 If 605 ml of a 50 % v/v solution is diluted to 2200 ml , what is the percent strength of the diluted solution?
3 If 240 ml of a 1 : 336 (w/v) solution is diluted to 700 ml, what is the ratio strength of the new solution?
4 If 23 ml of a 3.00 % nasal spray was diluted with 12 ml of normal saline solution, what would be the final drug concentration?
5 How many milliliters of a 25 % elixir can be prepared from 50 ml of a 56 % elixir?
6 If a cough syrup contains 21 mg of a drug in each teaspoonful, how many mg of drug needs to be added to a 60 ml container of the syrup to make the concentration 5 mg/ml?
7 What is the percentage strength (v/v) of an alcohol mixture that has a mix of 400 ml of 30 % alcohol, 225 ml of 55 % alcohol, and 150 ml of 15 % alcohol?
8 A pharmacist combines 10 pints of a 5 % w/v povidone-iodine solution with 7 quarts of 10 % w/v povidone-iodine solution. What is the strength of the resulting solution?
9

How many milliliters of 6 % and a 15 % solution do you need to prepare 2 gallon of 11 % solution?

10

What proportion of 10 % zinc oxide and 85 % zinc oxide do you need to make 65 % zinc oxide?

11

How many grams of 5 % hydrocortisone cream be mixed with 860 g of 0.25 % hydrocortisone cream to make a 4.00 % hydrocortisone cream?

12

How many milliliters of water should be added to 2.25 L of 1: 1500 w/v solution to make a 1: 6700 w/v solution?

13

How many grams of a 5.00 % w/w benzocaine ointment can be prepared by diluting 1 lb of a 30 % w/w benzocaine ointment with white petrolatum?

14

How many milliliters of a 16 % w/v stock solution benzalkonium chloride should be used in preparing the following prescription?

Benzalkonium chloride solution 220 ml
Make a solution such that
10 ml diluted to 1 L equals a 1: 2100 w/v solution
Sig : 10 ml diluted to a liter for external use

15

How many milliliters of 85 % (w/w) lactic acid with a specific gravity of 1.21 be used to prepare 300 ml of 42 % (w/v) lactic acid solution?

16

What is the specific gravity of a mixture containing 200 ml of water, 900 ml of glycerin having a specific gravity of 1.25, and 1300 ml of alcohol having a specific gravity of 0.81?

17

How many milliliters of a syrup having a specific gravity of 1.47 should be mixed with 1000 mL of a syrup having a specific gravity of 1.27 to obtain a product having a specific gravity of 1.30?

Answers

The Answer to question 1 is: 587.78 ml

The Answer to question 2 is: 13.75 % v/v

The Answer to question 3 is: 1 : 980

The Answer to question 4 is: 1.97 %

The Answer to question 5 is: 112.00 ml

The Answer to question 6 is: 48.00 mg

The Answer to question 7 is: 34 % v/v

The Answer to question 8 is: 7.92 % w/v

The Answer to question 9 is: 4205.56 ml of 15 % , 3364.44 ml of 6 %

The Answer to question 10 is: 4 : 11

The Answer to question 11 is: 3225.00 grams

The Answer to question 12 is: 7800.00 ml

The Answer to question 13 is: 2724.00 grams

The Answer to question 14 is: 65.48 ml

The Answer to question 15 is: 122.51 ml

The Answer to question 16 is: 0.99

The Answer to question 17 is: 176.47 ml