Question

What mass of \(\mathrm{KNO}_{3}\) is required to prepare \(125 \mathrm{~g}\) of \(1.5 \% \mathrm{KNO}_{3}\) solution?

Short answer

To prepare a 125 g solution with a 1.5% KNO3 concentration, you will need 1.875 g of KNO3.

Step-by-step solution

1. Identify the given information

Mass of the solution = 125 g Percentage of KNO3 in the solution = 1.5%

2. Apply the formula to find the mass of KNO3

Mass of KNO3 = (Percentage of KNO3 × Mass of Solution) / 100

3. Plug in the given values into the formula

Mass of KNO3 = (1.5 × 125) / 100

4. Calculate the mass of KNO3

Mass of KNO3 = 1.875 g So, 1.875 g of KNO3 is required to prepare a 125 g solution with 1.5% KNO3 concentration.

Key concepts

Molarity and Solution Preparation

Understanding molarity is crucial for anyone working with chemical solutions, as it is a measure of concentration that relates the amount of solute to the volume of solution. In simpler terms, molarity tells us how many moles of a substance are present in one liter of solution. To express this relationship, we use the formula:
\[ M = \dfrac{n}{V} \]
where \( M \) is the molarity, \( n \) is the number of moles of the solute, and \( V \) is the volume of the solution in liters.
When preparing a solution with a specific molarity, scientists must accurately measure the mass of the solute and dissolve it in a precise volume of solvent. The process usually involves using a balance to weigh the solute, a volumetric flask to measure the solvent, and possibly heat or agitation to aid in dissolution.

Tips for Accurate Solution Preparation

• Always use a clean, dry container to avoid contamination and ensure accurate measurements.
• When transferring your solute to the volumetric flask, use a funnel to avoid spillage.
• If dealing with a solid, make sure it is fully dissolved before making up the solution to the mark on the volumetric flask.

Consider the exercise provided, molarity is not directly used, but the mass needed to create a certain percentage concentration is a fundamental skill, which is also applicable to molarity calculations.

Stoichiometry in Chemistry

Stoichiometry is the mathematical relationship between the reactants and products in a chemical reaction. It's a way of quantifying the changes that occur during a reaction, and it's based on the law of conservation of mass which states that matter can neither be created nor destroyed.
We often use stoichiometry to convert between grams, moles, and molecules, to calculate yields, and to determine how much of each reactant is necessary for a reaction to proceed to completion. The balanced chemical equation provides the ratios (also known as stoichiometric coefficients) that tell us how molecules of each substance interact.

Applying Stoichiometry

• Be sure the chemical equation is balanced before performing stoichiometric calculations.
• To determine the amounts of products that can be formed, use the mole ratio from the balanced equation.
• Remember to consider the limiting reactant—the substance that will be used up first, thus determining the amount of product formed.

In context with the exercise, understanding stoichiometry is not immediately necessary, but recognizing the proportional relationships helps in more complex scenarios where you may need to calculate the mass of a reactant or product given other quantities.

Chemical Solution Formulas

Chemical solution formulas are essential for representing the concentration of solutions in chemistry. A common way to express concentration is through percent concentration, which indicates the amount of solute in a given amount of solution mass or volume. Percent concentration is calculated using the formula:
\[ \text{Percent Concentration} = \left( \dfrac{\text{Mass of Solute}}{\text{Mass of Solution}} \right) \times 100 \%\]
This tells us how many grams of solute are present per 100 grams or milliliters of solution. For weight/volume percent concentration, the denominator is the volume of the solution, useful when dealing with liquid solutes.

Calculating Percent Concentration

• Use an accurate scale to weigh your solute.
• Measure or calculate the total mass or volume of your solution carefully.
• Apply the percent concentration formula to find the mass or volume of the solute required for a desired concentration.

In relation to the exercise given, once the percent concentration is known, figuring out the mass of solute needed becomes a straightforward calculation, bridging the gap between conceptual understanding and practical application.