Question

If $67.1\mathrm{g}$ of ${\mathrm{CaCl}}_2$ is added to $275\mathrm{g}$ of water, calculate the mass percent of ${\mathrm{CaCl}}_2$ in the solution.

Short answer

The mass percent of CaCl₂ in the solution is approximately 19.6%.

Step-by-step solution

Calculate the total mass of the solution

To find the total mass of the solution, we just need to add the mass of the solute (CaCl₂) and the mass of the solvent (water). Total mass = Mass of CaCl₂ + Mass of water Total mass = 67.1 g + 275 g

Calculate the mass percent of CaCl₂

Now, we can plug our values into the mass percent formula. Mass percent of CaCl₂ = (Mass of CaCl₂ / Total mass of the solution) * 100 Mass percent of CaCl₂ = (67.1 g / (67.1 g + 275 g)) * 100 Now, calculate the mass percent of CaCl₂: Mass percent of CaCl₂ ≈ 19.6% So, the mass percent of CaCl₂ in the solution is approximately 19.6%.

Key concepts

Chemistry Education

Understanding the fundamental concepts in chemistry is crucial for students to advance in their studies and to grasp everyday applications of this science. Mass percent calculation, for example, is a basic concept that arises often not only in laboratory work but also in practical activities such as cooking or medication preparation.

Incorporating real-life examples into the education process can significantly enhance comprehension. Imagine you're making a salt solution to gargle with - knowing how to calculate the mass percent tells you exactly how much salt you've added relative to the total mass of the solution, ensuring its effectiveness without being too abrasive.

To educate on this topic, one must ensure that the student understands the definition of terms like solute (the substance being dissolved), solvent (the substance doing the dissolving), and the solution itself. This context helps demonstrate the relevance and application of the mass percent concept in various scenarios.

Solutions Concentration

The concentration of a solution is a measurement of how much solute is dissolved in a given quantity of solvent or solution. There are several ways to express concentrations including molarity, molality, and mass percent.

Mass percent is particularly useful because it's simple to understand: it's the mass of the solute divided by the total mass of the solution, multiplied by 100. It's commonly used because it's independent of temperature, unlike volume-based measurements that can change with thermal expansion or contraction.

When preparing solutions in a lab or other settings, knowing the concentration allows for precision and reproducibility. For students, understanding how to calculate mass percent reinforces concepts like ratios and proportions, both of which are foundational in chemistry and other fields of science.

Stoichiometry

Stoichiometry is an area of chemistry that involves calculating the quantities of reactants and products involved in chemical reactions. It's based on the conservation of mass and the principle that atoms are neither created nor destroyed in chemical reactions.

Mass percent calculations play a pivotal role in stoichiometry as they help determine the purity of a substance or the composition of a mixture, which is essential for calculating the amounts of reactants needed. The understanding of stoichiometry equips the student to tackle more complex problems involving chemical equations, reactant-to-product conversions, and limiting reagents.

Students can improve their problem-solving skills in stoichiometry by practicing with mass percent calculations, as it mirrors the logical steps required to solve a wide array of stoichiometric problems.