Lesson · C.3.1

Solutions and concentration

How to name a solution's parts and calculate percent and molar concentration, the two ways the HESI A2 Chemistry subtest asks you to describe how much solute is in a solution.

ObjectiveC.3.1Read4 minExam weightQuantitative Chemistry ≈ 24% of Chemistry

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What you will be able to do

  • Name the solute and solvent in a mixture and classify it as dilute, concentrated, or saturated.
  • Calculate percent concentration (weight per volume, volume per volume, weight per weight) from a word problem.
  • Calculate molarity and use the dilution equation to find a missing concentration or volume.

What the lesson concludes

  • A solution is a homogeneous mixture: one substance (the solute) is dissolved throughout another (the solvent), and you cannot see the two parts separately.
  • Percent concentration expresses solute per 100 parts of solution, most often as weight per volume (g per 100 mL) for a solid dissolved in a liquid.
  • Molarity (mol/L) counts particles rather than mass, which is why medication and lab values often report both a percentage and a molar or millimolar concentration.
  • The dilution equation, concentration one times volume one equals concentration two times volume two, lets you find any one of four values once you know the other three.
  • Saline and dextrose fluids on a med-surg unit are everyday percent-concentration solutions, which is why this objective shows up dressed as a clinical scenario.