Determine the amount in grams of KCl that exists in 20.3g of a solution that contains 1.14% KCl by mass.
The Correct Answer and Explanation is:
To determine the amount of KCl in the solution:
Given:
- Total mass of the solution = 20.3 g
- Mass percent of KCl = 1.14%
Step-by-step solution:
Use the formula:Mass of solute (KCl)=Mass percent of solute100×Mass of solution\text{Mass of solute (KCl)} = \frac{\text{Mass percent of solute}}{100} \times \text{Mass of solution}Mass of solute (KCl)=100Mass percent of solute×Mass of solution
Substitute the given values:Mass of KCl=1.14100×20.3=0.0114×20.3=0.23142 g\text{Mass of KCl} = \frac{1.14}{100} \times 20.3 = 0.0114 \times 20.3 = 0.23142 \, \text{g}Mass of KCl=1001.14×20.3=0.0114×20.3=0.23142g
Final Answer:
0.231 grams of KCl
Explanation
In a chemical solution, the mass percent composition describes the concentration of a solute (the substance being dissolved) relative to the total mass of the solution. It tells you how many grams of the solute are present in every 100 grams of the solution. In this case, potassium chloride (KCl) is the solute, and the solution has a mass percent of 1.14%, meaning that for every 100 grams of the solution, 1.14 grams of KCl are present.
To find out how many grams of KCl are contained in 20.3 grams of this solution, we multiply the total mass of the solution by the fraction that represents the mass percent of KCl. Since 1.14% is equal to 1.14 divided by 100, we convert the percentage to a decimal before multiplying. Multiplying the decimal by the total solution mass gives the exact mass of KCl in the sample.
The arithmetic involves straightforward multiplication: 0.0114 multiplied by 20.3. The result is approximately 0.23142 grams. Since we are typically asked to round based on the precision of the given values, the final answer is rounded to three significant figures, giving 0.231 grams of KCl.
This type of calculation is useful in laboratory work, where precise measurements of chemical components are necessary. It also illustrates how mass percent can quickly provide an estimate of solute content in mixtures.
