Pharmacy Concentration Expressions Quiz

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Questions and Answers

What does a percentage concentration of 10% w/v indicate?

10 mL of drug in every 100 mL of solution

10 g of drug in every 10 mL of solution

10 g of drug in every 100 mL of solution (correct)

10 g of drug in every 100 g of solution

Which concentration expression is appropriate for a liquid ingredient mixed with a solid vehicle?

% v/v

% v/w

% w/v

% w/w (correct)

When converting percent strength to ratio strength, which of the following is true?

A higher percent strength equals a lower ratio strength

Percent strength of 5% is equivalent to a ratio strength of 1:20 (correct)

The ratio strength is numerically equal to the percent strength

Percent strength can only be converted to ratio strength for solid preparations

What does a concentration expressed as w/v typically represent?

Weight of the drug per volume of solvent Signup and view all the answers

In a pharmaceutical preparation, the choice of calculation basis depends primarily on what factor?

The state of the dosage form Signup and view all the answers

What is the correct interpretation of 10% w/w in a preparation?

10 g of drug per 100 g of total preparation Signup and view all the answers

When a powdered substance is dissolved in a liquid vehicle, which concentration calculation is generally used?

Weight-in-volume (w/v) Signup and view all the answers

In the ratio strength expression, what does a ratio of 1:100 indicate?

1 part drug per 100 parts product Signup and view all the answers

Which of the following best describes the fundamental concept of concentration?

It is the ratio of an ingredient to an amount of product Signup and view all the answers

What does ratio strength express?

The parts of active drug relative to the total number of parts of the product Signup and view all the answers

If 2 mg of a drug is present in a 1 mL solution, what is the ratio strength (w/v) of the solution?

1:1000 Signup and view all the answers

To prepare 240 g of a 5% (w/w) solution, how much phenol is needed?

12 g Signup and view all the answers

Convert 4% w/v to mg/mL.

40 mg/mL Signup and view all the answers

How many grams of dextrose are needed for 4000 mL of a 5% solution?

200 g Signup and view all the answers

What does ppm mean in concentration terms?

Parts per million Signup and view all the answers

If a solution has a ratio strength of 1:10,000, what would its concentration be in mg/mL?

0.01 mg/mL Signup and view all the answers

Expressing 0.02% as ratio strength results in which representation?

1:10000 Signup and view all the answers

Which of the following is NOT a way to express concentration?

Molarity (mol/L) Signup and view all the answers

What is the expression for the strength of very dilute solutions typically called?

Parts Per Million (PPM) Signup and view all the answers

Study Notes

Concentration Expressions

Concentration is the ratio of the amount of an ingredient to the amount of the product.
Concentration can be expressed in various ways depending on the ingredients and product.

Objectives

Define percent weight-in-volume, percent volume-in-volume, and percent weight-in-weight.
Define ratio strength.
Convert percent strength to ratio strength and vice versa.
Calculate percentage strength and ratio strength of a pharmaceutical preparation.
Use percent strength and ratio strength to calculate the amount of an ingredient present in a pharmaceutical preparation.
Use percent and ratio strength to calculate the amount of an ingredient needed in compounding.

Concentration Basis

Solid in liquid (w/v): weight of solid in volume of liquid.
Liquid in solid (v/w): volume of liquid in weight of solid.
Liquid in liquid (v/v): volume of liquid in volume of liquid.
Solid in solid (w/w): weight of solid in weight of solid.

Percentage

Percentage describes the number of parts of active drug relative to 100 parts of the total.
Percentage must be accompanied by a description (e.g., w/w, w/v, v/v).
- % w/w: grams of active drug per 100 grams of product.
- % w/v: grams of active drug per 100 mL of product.
- % v/v: milliliters of active drug per 100 mL of product.
Examples:
- 10% w/v = 10 g of drug in every 100 mL of total.
- 10% w/w = 10 g of drug in every 100 g of total.

Special Considerations in Percentage Calculations

The nature of the ingredients determines the calculation basis.
- Powders dissolved in liquids (w/v).
- Powders mixed with solids/semisolids (w/w).
- Liquids in liquids (v/v).
Weight may need to convert to volume or vice versa (using specific gravity).
- g = mL × specific gravity
- mL = g / specific gravity

Ratio Strength

Ratio strength expresses concentration as parts of active drug relative to any number of parts of the whole.
Ratio strength is expressed as 1 part active drug : total parts.
Example: 1:1000 w/v means 1 part active drug in 1000 parts of total.

Percentage and Ratio Strength Interconversion

Example: Convert 0.02% to ratio strength (1:5000).
Example: Convert 1:4000 to percentage strength (0.025%).

Other Concentration Expressions

Milligram per milliliter (mg/mL).
Parts per million (ppm).
Converting percentages to mg/mL and ppm.

Example Calculations

Specific examples (weight-in-volume, volume-in-volume, weight-in-weight) are provided demonstrating calculations for various concentrations.

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Description

Test your understanding of concentration expressions in pharmaceuticals. This quiz covers various methods of expressing concentration, including percent weight-in-volume, volume-in-volume, and weight-in-weight. Additionally, you'll learn to convert strengths and calculate ingredient amounts for pharmaceutical preparations.