Calculations Exam 1 - Practice Questions from Pre-Class Handouts

How many grams of potassium permanganate should be used in compounding the following prescription?

Potassium Permanganate 0.01%

Purified Water ad 200 mL

Sig. as directed.

0.02 g

How many milliliters (one decimal place) of liquefied phenol should be used in compounding the following prescription?

Liquefied Phenol 3.5%

Calamine Lotion ad 350 mL

Sig. For External Use

12.3 mL

How many milligrams (one decimal place) of hydrocortisone should be used in compounding the following prescription?

Hydrocortisone 1/6%

Hydrophilic ointment ad 20 g

Sig. Apply

33.3 mg

If a volume of 16 mL of liquid phenol is combined with 100 mL of water (Note: both liquids are miscible and no volume contraction/expansion occurs on combination). What is the percent strength of this solution? Report appropriate units.

13.79% v/v

Express the ratio 1:1000 as a percentage.

0.1%

Express 0.004% as ratio strength.

1:25,000

How many milligrams of hexachlorophene should be used in compounding the following prescription?

Hexachlorophene 1:400

Hydrophilic Ointment ad 20 g

Sig. Apply

50 mg

If there were 60 mcg of drug in each 500 mL of blood, express

its concentration in mg%

0.01 mg%

The EPA has set the maximum contaminant level (MCL) for mercury in drinking water at 0.002 mg/L. What is this concentration in ppm?

0.002 ppm

The EPA has set the maximum contaminant level (MCL) for mercury in drinking water at 0.002 mg/L. What is this concentration in ppb?

2 ppb

If a fluid ounce of a certain liquid weighs 40 g, what is the specific gravity of the liquid?

1.353

What is the weight, in grams, of 4 fl. oz. of a liquid having a specific gravity of 1.118?

132.237 g

If fifty glycerin suppositories are made from the following formula, how many milliliters of glycerin, having a specific gravity of 1.25, would be used in the preparation of 96 suppositories?

Glycerin 91 g

Sodium stearate 9 g

Purified water 5 g

139.776 mL

From the following formula, calculate the quantity of each ingredient required to make 100 mL of calamine lotion.

Calamine 80 g

Zinc Oxide 80 g

Glycerin 20 g

Bentonite Magma 250 mL

Calcium Hydroxide Topical Solution, to make 1000 mL

Calamine 8 g

Zinc Oxide 8 g

Glycerin 2 g

Bentonite Magma 25 mL

Calcium Hydroxide Topical Solution, to make 100mL

From the following formula for one rectal suppository, calculate the quantity of each ingredient to prepare 20 such suppositories:

Promethazine Hydrochloride 25 mg

Ascorbyl palmitate 1%

White wax 5%

Cocoa butter ad 2 g

Promethazine Hydrochloride 0.5 g

Ascorbyl palmitate 0.4 g

White wax 2 g

Cocoa butter 37.1 g

Following is a formula for a prescription

Coal tar 5 parts

Zinc Oxide 15 parts

Hydrophilic ointment 70 parts

What quantities would be necessary to make 90 g?

Coal tar 5 g

Zinc oxide 15 g

Hydrophilic ointment 70 g

If 500 mL of a 15% v/v solution is diluted to 3 L, what is the % strength of the new solution?

2.5% v/v

How many milliliters of a 1:5000 w/v solution of the preservative lauralkonium chloride can be made from 250 mL of a 0.4% solution? How much of the diluent must be added?

5000 mL

4750 mL

How many milliliters of a 1:800 w/v stock solution should be used to make 4 liters of a 1:4000 w/v solution?

800 mL

How much drug should be used in preparing 50 mL of a solution such that 5 mL diluted to 500 mL will yield a 1:1000 solution?

5 g

How much water should be mixed with 4000 mL of 85% v/v alcohol to make 50% v/v alcohol ?

enough to make 6800 mL, >2800 mL

How much water should be added to 5000 g of 90% w/w alcohol to make 40% w/w alcohol?

6250 g

How many milliliters of 37% w/w hydrochloric acid having a specific gravity of 1.20 are required to make 1000 mL of diluted hydrochloric acid 10% w/v?

225.22 mL

If 30 g of a 1% hydrocortisone ointment were diluted to 60 g with Vaseline, what would be the concentration of hydrocortisone in the mixture?

0.5%

Convert 10 fl. oz. to mL

296 mL

Colcrys tablets contain 0.8 mg of colchicine, used in the treatment of gout.

i) What is the mass of drug contained in each tablet in grains (up to 3 decimal places)?

ii) How many of these tablets can be manufactured from 4 oz of colchicine?

i) 0.012 gr

ii) 141750 tablets

If a child accidentally swallowed 1.7 fluid ounces of FEOSOL Elixir, containing 2/3 gr of ferrous sulfate per 5 mL, how many milligrams (to the nearest hundredth) of ferrous sulfate did the child ingest?

435.66 mg

Convert 16°C to corresponding degrees Fahrenheit

60.8 °F

A prescription calls for 900 milligrams of a substance. After weighing this amount on a balance, the pharmacist decides to check by weighing it again on a more sensitive balance, which registers only 840 milligrams. Because the first weighing was 60 milligrams short of the desired amount, what was the percentage of error?

6.67%

Using a graduated cylinder, a pharmacist measured 40 milliliters of a liquid. On subsequent examination, using a narrow-gauge burette, it was determined that the pharmacist had actually measured 42 milliliters. What was the percentage of error in the original measurement?

5%

What is the smallest quantity (round to whole mg) that can be weighed on a prescription balance if the acceptable error (or sensitivity requirement) is 6 mg and the % of error is 4%?

150 mg