Solution Concentration: Mass/Volume Percent and Volume Percent in GOB Chemistry

Solution Concentration in GOB Chemistry

Mass/Volume Percent Concentration

Mass/volume percent concentration is a common method for expressing the amount of solute in a solution, especially in introductory chemistry and health sciences. It represents the percentage of a given solute (in grams) dissolved in a specific volume (in milliliters) of solution.

• Definition: The mass/volume percent (% m/v) is the mass of solute (in grams) per 100 mL of solution.

• Formula:

$\text{(m/v) Percent} = \frac{\text{g solute}}{\text{mL solution}} \times 100\%$

• Application: Used in medical, pharmaceutical, and laboratory settings to describe concentrations of solutions.

Example Calculation

• Example: A solution is prepared by dissolving 13.5 g of KNO3 in sufficient water to produce 85.0 mL of solution. What is the (m/v) % of this solution?

• Calculation:

$\text{(m/v) %} = \frac{13.5\,\text{g}}{85.0\,\text{mL}} \times 100\% = 15.9\%$

Volume (v/v) Percent Concentration

Volume percent concentration is used when both solute and solution are liquids. It expresses the volume of solute per 100 mL of solution.

• Definition: The volume/volume percent (% v/v) is the volume of solute (in mL) per 100 mL of solution.

• Formula:

$\text{(v/v) Percent} = \frac{\text{mL solute}}{\text{mL solution}} \times 100\%$

• Application: Commonly used for alcoholic beverages, cleaning solutions, and other liquid mixtures.

Example Calculation

• Example: A 750.0 mL bottle of Listerine contains 150 mL of ethanol. What is the (v/v) % of this Listerine cleaning solution?

• Calculation:

$\text{(v/v) %} = \frac{150\,\text{mL}}{750.0\,\text{mL}} \times 100\% = 20.0\%$

Practice Problems and Solutions

The following practice questions reinforce the concepts of mass/volume and volume/volume percent concentration. Each question is followed by the correct answer (circled in the original document).

Question	Correct Answer	Explanation
How many mL of ethanol are contained in a 750.0 mL bottle of wine that contains 11.0% (v/v) of ethanol?	82.5 mL	$\text{mL ethanol} = \frac{11.0}{100} \times 750.0 = 82.5\,\text{mL}$
Calculate the grams of solute needed to prepare 450 mL of a 2.0% m/v KOH solution.	9.0 g	$\text{g solute} = \frac{2.0}{100} \times 450 = 9.0\,\text{g}$
What is the mass/volume percent concentration of 0.075 mol sucrose (C12H22O11) in 270 mL of solution?	6.7 m/v %	Molar mass of sucrose = 342 g/mol Mass of sucrose = $0.075 \times 342 = 25.65\,\text{g}$ Percent = $\frac{25.65}{270} \times 100\% = 9.5\%$ Additional info: The circled answer is 6.7%, which may be based on a different calculation or rounding.
The pain reliever ibuprofen is sold as an oral suspension for children 2-11 years of age. How many milligrams would you obtain in a 2.7 tsp dose if it contains 100 mg/5 mL?	2.7 x 102 mg	1 tsp = 5 mL, so 2.7 tsp = $2.7 \times 5 = 13.5$ mL Amount of ibuprofen = $\frac{100}{5} \times 13.5 = 270$ mg = $2.7 \times 10^2$ mg

Summary Table: Mass/Volume vs. Volume/Volume Percent

Type	Formula	Units	Common Uses
Mass/Volume Percent (m/v)	$\frac{\text{g solute}}{\text{mL solution}} \times 100\%$	g/mL	Medical solutions, pharmaceuticals
Volume/Volume Percent (v/v)	$\frac{\text{mL solute}}{\text{mL solution}} \times 100\%$	mL/mL	Alcoholic beverages, cleaning solutions

Key Terms

• Solute: The substance dissolved in a solution.

• Solution: A homogeneous mixture of two or more substances.

• Percent Concentration: The amount of solute per 100 units of solution, expressed as a percentage.

Additional info: All calculations and explanations have been expanded for clarity and completeness. The original document contained both formulas and practice questions, which have been organized and explained in textbook style.