A scientist mixes 40 mL of a 10% saline solution with 60 mL of a 20% saline solution. What is the concentration of the resulting solution?
Title: How to Calculate the Concentration of a Mixed Saline Solution: A Scientific Approach
When mixing saline solutions of different concentrations, understanding how to compute the resulting concentration is essential in laboratory, medical, and educational settings. A common challenge is determining the final concentration when combining measured volumes of solutions with known salt (solute) percentages. In this article, we explore a precise method using a practical example: mixing 40 mL of a 10% saline solution with 60 mL of a 20% saline solution. The result? A clearer understanding of concentration calculations that combines chemistry and arithmetic.
Step-by-Step Breakdown: How to Find the Final Concentration
To find the concentration of the mixed solution, we use the principle of mass balance—the idea that the total amount of solute before mixing equals the total amount after mixing, regardless of volume or concentration.
Given:
- Volume of 10% saline solution: 40 mL
- Concentration of 10% solution: 10% = 0.10
- Volume of 20% saline solution: 60 mL
- Concentration of 20% solution: 20% = 0.20
Step 1: Calculate the amount of salt in each solution
For a solution, concentration (%) = (mass of solute / mass of solution) × 100, but we can also work directly with volumes and concentrations for a straightforward calculation.
Salt mass from first solution: (10 / 100) × 40 mL = 0.10 × 40 = 4 grams of salt
Salt mass from second solution: (20 / 100) × 60 mL = 0.20 × 60 = 12 grams of salt
Step 2: Add the total salt and total volume
Total salt = 4 grams + 12 grams = 16 grams Total volume = 40 mL + 60 mL = 100 mL
Step 3: Calculate the final concentration
Concentration = (Total salt mass / Total volume) × 100 = (16 g / 100 mL) × 100 = 16%
Final Answer:
The resulting solution has a 16% saline concentration.
Why This Method Matters
This calculation reflects the law of conservation of mass applied in solution chemistry. It helps scientists, medical professionals, and students accurately prepare and verify saline solutions for experiments, medical treatments, or educational demonstrations. Understanding concentration mixing is foundational in fields such as biology, pharmacy, and chemical engineering.
Pro Tip: Use strategic mixing principles every time
Whether scaling up for large batches or small lab work, building a habit of mass (or volume) conservation ensures reliability in your results. Mixing solutions isn’t just about adding volumes—it’s about preserving the balance of matter.
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Meta Description: Discover how to accurately calculate the concentration of mixed saline solutions. Learn from a real-world example: mixing 40 mL of 10% saline with 60 mL of 20% saline. Step-by-step guide with full explanation.
If you're interested in precise solutions, understanding exact concentrations empowers accurate scientific work—one drop at a time.
