A chemist has 250 grams of a 40% saline solution. She wants to increase the concentration to 60% by evaporating some water. How many grams of water must she evaporate? - Parker Core Knowledge

Understanding the Context

Saline solutions are foundational in medicine, food processing, and manufacturing, where concentration directly influences performance. With rising operational costs and tight supply conditions, small efficiency gains matter. Evaporating water to concentrate salt solutions presents a low-tech yet scientifically grounded strategy that aligns with sustainability trends—reducing waste by minimizing water use and maximizing value per batch. In the U.S., where informed DIY and warehouse smartness thrive, especially on mobile devices, this problem resonates beyond labs. Awareness grows through shared guides, video tutorials, and community forums focused on chemistry fundamentals—making residents curious about real-world applications they might encounter or replicate. This organic interest fuels demand for clear, trustworthy answers like the one readers seek.

How A Chemist Can Increase Saline Concentration by Evaporating Water

The key lies in understanding concentration as the ratio of salt to total solution mass. With 250 grams at 40% strength:

• Salt mass = 40% of 250 grams = 100 grams
• Water mass = total mass – salt mass = 250g – 100g = 150 grams

Key Insights

To reach a 60% saline solution, salt (100g) must make up 60% of the final mixture. Let x be the grams of water to evaporate. After evaporation:

• Final mass = 250g – x
• Salt concentration = 100g / (250g – x) = 60%

Solving:
100 = 0.6 × (250 – x)
100 = 150 – 0.6x
0.6x = 50
x ≈ 83.33 grams

Rounding, evaporation of approximately 83 grams removes the optimal amount of water, raising salinity to 60%. This approach reflects widely taught principles in chemistry—concentration through mass balance—making it a reliable method chemists trust even when refining lab samples.

Common Questions About This Concentration Challenge

Final Thoughts

Q: How does evaporation affect solution purity?
A: Evaporating water increases concentration without adding chemicals, preserving solution