Question

What is the difference between a \(10 \%(\mathrm{v} / \mathrm{v})\) methyl alcohol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right)\) solution and a \(10 \%(\mathrm{~m} / \mathrm{m})\) methyl alcohol solution?

Short answer

10% (v/v) is based on volume, while 10% (m/m) is based on mass.

Step-by-step solution

- Understand the Notations

First, recognize what 10% (v/v) and 10% (m/m) mean: - 10% (v/v) is a volume/volume percentage and represents 10 mL of methyl alcohol in every 100 mL of solution. - 10% (m/m) is a mass/mass percentage and represents 10 grams of methyl alcohol in every 100 grams of solution.

- Calculate Volume for 10% (v/v) Solution

Consider 100 mL of a 10% (v/v) methyl alcohol solution. This solution contains 10 mL of methyl alcohol and 90 mL of water. This concludes the distribution of volumes.

- Calculate Mass for 10% (m/m) Solution

Consider 100 grams of a 10% (m/m) methyl alcohol solution. This solution contains 10 grams of methyl alcohol and 90 grams of water. Here, we account for the weights instead of the volumes.

- Compare Solutions

In summary: - A 10% (v/v) solution involves the volume of the solute and solvent.- A 10% (m/m) solution involves the mass of the solute and solvent. The difference lies in whether the percentage is given by volume or by mass.

Key concepts

Volume/Volume Percentage

Let's explore volume/volume percentage (v/v%). This notation is often used in chemistry to describe the concentration of a solution. It explains how much volume of a solute is present in a certain volume of the solution. Specifically,
a 10% (v/v) solution signifies that there are 10 milliliters (ml) of solute (in this case, methyl alcohol \ \(CH_3OH\ \)) in every 100 milliliters of the solution.
This type of concentration is particularly useful when dealing with liquid solutes and solvents.
Let's break it down step-by-step:

• First, measure out 10 mL of methyl alcohol.
• Add this 10 mL to a container.
• Then, add enough water to make the total solution volume up to 100 mL.

Now, you have a 10% (v/v) methyl alcohol solution. It's essential to remember that in v/v% calculations, both the solute and solvent volumes add up to the final volume.
This concept is straightforward and is used for preparing solutions in various scientific and everyday applications.

Mass/Mass Percentage

Now, let's look at mass/mass percentage (m/m%). This notation indicates how much mass of a solute is present in a given mass of the solution. For a 10% (m/m) solution, it means there are 10 grams of methyl alcohol in every 100 grams of the solution. Understanding m/m% is crucial when dealing with solid or liquid solutes in a solution.
Here’s the process:

• Measure and weigh 10 grams of methyl alcohol.
• Place it in a container.
• Add enough water until the total mass of the mixture is 100 grams.

By doing this, you create a 10% (m/m) solution.
Remember, in mass/mass percentage calculations, the masses of both the solute and the solvent combine to give the total mass.
This method is especially useful in laboratory practices where precise mass measurements are required.

Solution Composition

Understanding solution composition is essential to mastering the topic of concentration calculations. The concept revolves around how a solute (substance being dissolved) interacts with the solvent (substance doing the dissolving). Here are a few points to clarify this:

A solution is simply a homogeneous mixture of two or more substances.

The solute is the part that gets dissolved (e.g., methyl alcohol).

The solvent is the part that dissolves the solute (e.g., water).

Whether working with volume/volume or mass/mass percentages, always remember that the concentration represents the ratio of solute to the solution.
It's also important to note that temperature and pressure can impact the overall composition and properties of a solution.
In practice, the concept of solution composition helps in various fields, including chemistry, biology, medicine, and engineering. For students, grasping this area lays a solid foundation for further studies and practical applications.