Problem 13 - Chemistry Matter and Change

Question

What is the percent by volume of ethanol in a solution that contains 35 mL of ethanol dissolved in 155 mL of water?

Step-by-Step Solution

Answer

The percent by volume of ethanol in the solution is approximately 18.42%. This is calculated using the formula: Percent by volume = \(\frac{volume\:of\:solute}{total\:volume\:of\:solution}\) * 100, where we have a volume of ethanol (solute) of 35 mL and a total volume of the solution of 190 mL (35 mL + 155 mL).

Step 1: Determine the total volume of the solution.

In order to calculate the percent by volume of ethanol, we first need to determine the total volume of the solution. We can find this by adding the volume of ethanol (35 mL) and the volume of water (155 mL). Total volume = volume of ethanol + volume of water

Step 2: Calculate the percent by volume of ethanol.

Now that we have the total volume, we can use the formula for calculating the percent by volume: Percent by volume = (volume of solute / total volume of solution) * 100 Substitute the known values in the equation: Percent by volume = (35 mL / (35 mL + 155 mL)) * 100

Step 3: Simplify and solve.

Simplify the equation and solve for the percent by volume: Percent by volume = (35 mL / 190 mL) * 100 Now, divide 35 by 190: Percent by volume = (0.1842) * 100 Finally, multiply the result by 100 to get the percentage: Percent by volume ≈ 18.42% The percent by volume of ethanol in the solution is approximately 18.42%.

Key Concepts

Understanding Ethanol Solutions

An ethanol solution is a mixture where ethanol is one of the substances dissolved in another substance, typically a liquid like water. Ethanol, also known as alcohol, is commonly used in various solutions due to its solubility and effectiveness as a solvent. In this context, the term "solution" refers clearly to the homogeneous mixture formed when a solute, in this case, ethanol, is dissolved in a solvent, such as water.

When we talk about ethanol solutions, we're often interested in how much ethanol is present in the solution compared to the total amount of solution. This is crucial in applications like chemical manufacturing, beverages, and even pharmaceutical preparations. Understanding ethanol solutions also involves knowing that different concentrations can have significant effects, which is why calculating the concentration is essential in chemistry.

• Ethanol is a solute when mixed with water.
• Water is the solvent in ethanol solutions.
• Such solutions are homogeneous, meaning the composition is uniform throughout.

The Basics of Solution Concentration

Solution concentration is a measure of how much of a solute is present in a solution compared to the whole solution. In our example, the ethanol solution comprises both ethanol and water. Here, we are specifically calculating the percent by volume, which is a common way to express concentration for liquid solutions.

Percent by volume is calculated using the formula:\[\text{Percent by volume} = \left( \frac{\text{Volume of solute}}{\text{Total volume of solution}} \right) \times 100\]This equation tells us the ratio of the volume of the solute (ethanol) to the total volume of the solution, multiplied by 100 to convert it to a percentage.

This method is very handy in situations where the densities of the solute and solvent are similar, as it directly deals with volumes rather than needing to convert to mass or moles. Knowing how to directly compute the concentration helps in ensuring the right proportions are mixed for various chemical recipes, thereby affecting the properties and behaviors of the final solution prepared.

• Ideal for solutions with similar component densities.
• Expresses concentration in volume percentage.

Performing Chemical Calculations

Chemical calculations, like determining the percent by volume, are foundational skills in chemistry that allow us to quantify the composition of solutions. These calculations are conducted step-by-step to ensure clarity and accuracy, as seen in the provided solution.

In the calculation for percent by volume: - **Step 1:** First, determine the total volume by adding the volumes of all components (ethanol and water). - **Step 2:** Use the percent by volume formula to calculate ethanol's concentration. - **Step 3:** Simplify and solve to find the percentage value.
Knowledge of chemical calculations is essential for predicting how substances will interact with one another in various conditions. In practice, this includes everything from mixing safe chemical compounds in the lab to developing commercial products. By mastering these calculations, chemists are better equipped to formulate solutions with precise characteristics needed for specific purposes.

• Ensures accurate and safe chemical mixing.
• Essential for industrial and laboratory settings.