GED Science TestPhysical ScienceMedium
A chemist is preparing a solution by dissolving 25 grams of sodium chloride (NaCl) in 225 grams of water. What is the mass percent concentration of NaCl in this solution?
- A10%
- B9.1%
- C11.1%
- D25%
Show answer & explanationAnswer & explanation
Correct answer: A. 10%
Mass percent concentration is calculated as (mass of solute / mass of solution) * 100%. The mass of the solute (NaCl) is 25 g, and the mass of the solvent (water) is 225 g. The total mass of the solution is 25 g + 225 g = 250 g. So, (25 g / 250 g) * 100% = 10%.
Why the other options are wrong
- B. This results from dividing solute mass by solvent mass (25/225).
- C. This results from dividing solvent mass by solute mass (225/25) or similar incorrect calculation.
- D. This would be the concentration if the total solution mass was 100g and 25g was solute.
Mass Percent Concentration
Mass percent concentration is a way to express the concentration of a solution as the mass of solute divided by the total mass of the solution, multiplied by 100%.
- Formula: (mass of solute / mass of solution) * 100%
- Mass of solution = mass of solute + mass of solvent
- Expressed as a percentage
Memory trick: Solution's Strength: Solute's Slice of the Whole.