3 Practical Examples of Percent Concentration Calculations

Understanding Percent Concentration by Mass or Volume

In chemistry, percent concentration is a crucial concept used to express the amount of solute present in a solution relative to the total solution volume or mass. It is commonly utilized in various applications, from preparing solutions in a laboratory to understanding nutritional information in food products. This guide provides three practical examples of calculating percent concentration by mass or volume.

Example 1: Preparing a Saltwater Solution

In a laboratory setting, you may need to prepare a saltwater solution for experiments. Suppose you want to create a 10% (w/v) salt solution. This means you need 10 grams of salt for every 100 mL of solution.

To prepare this solution, you would:

• Measure out 10 grams of salt.
• Dissolve the salt in enough water to make the total volume up to 100 mL.
• The resulting solution will have a concentration of 10% (w/v), meaning it contains 10 grams of salt per 100 mL of solution.

Relevant Note: Percent concentration by mass/volume is commonly used in biological and chemical laboratories for preparing solutions. Ensure to use a precise balance for accurate measurement of the solute.

Example 2: Calculating the Concentration of a Sugar Solution

In the food industry, understanding the concentration of sugar in beverages is essential for nutritional labeling. Let’s say a manufacturer produces a fruit drink that contains 25 grams of sugar in every 250 mL of the drink.

To calculate the percent concentration by mass/volume, the formula is:

ext{Percent Concentration (w/v)} =

rac{ ext{mass of solute (g)}}{ ext{volume of solution (mL)}} imes 100

Substituting the values:

• ext{Percent Concentration} = (
  rac{25 ext{ g}}{250 ext{ mL}}) imes 100 = 10 ext{% (w/v)}

This means the fruit drink has a sugar concentration of 10% (w/v).

Variation: If the manufacturer wanted to create a sweeter version, they could adjust the amount of sugar. For example, increasing the sugar to 50 grams in the same volume would yield a 20% (w/v) concentration.

Example 3: Determining the Concentration of a Hydrochloric Acid Solution

When working in a laboratory, it is often necessary to know the concentration of acids used in various experiments. For instance, a lab technician prepares a dilute hydrochloric acid (HCl) solution by mixing 5 mL of concentrated HCl (which has a density of 1.19 g/mL) with enough water to make a total volume of 100 mL.

First, calculate the mass of the concentrated HCl:

• Mass = Volume × Density = 5 mL × 1.19 g/mL = 5.95 g

Next, calculate the percent concentration by mass/volume:

• ext{Percent Concentration (w/v)} =
  rac{5.95 ext{ g}}{100 ext{ mL}} imes 100 = 5.95 ext{% (w/v)}

This indicates that the dilute hydrochloric acid solution contains 5.95% HCl by mass/volume.

Note: Always handle concentrated acids with care and use proper personal protective equipment (PPE) when preparing solutions.