Understanding Percent Solutions in Chemistry

Aug 30, 2024

Laboratory Math: Percent Solution

Introduction

  • Short discussion on laboratory math.
  • Reporting scheduled for next week.
  • Attendance link and assignment will be provided after the video.

Reagents in Clinical Chemistry

  • Reagents include chemicals, standards, and types of waters.
  • Used for quality control and various purposes in clinical chemistry.

Percent Solutions

  • Laboratory reagents are expressed in:
    • Percent
    • Normality
    • Molarity
  • Focus today: Percent solution.
  • Required titer or dilution to reflect concentration; titer covered in part 3.

Definition of Percent Solution

  • Percent Solution: Amount of solute diluted in grams (solid) or milliliters (liquid) per 100 ml of solution.
  • Components:
    • Solute: Substance dissolved in a liquid.
    • Solvent: Liquid in which the solute is dissolved.

Types of Percent Solutions

  • Combinations of:
    • Solid solute + solid solvent
      • Example: Alloy metals
    • Solid solute + liquid solvent
      • Example: Powdered solutions
    • Liquid solute + liquid solvent
      • Example: Biological fluids (serum/plasma)

Solute and Solvent in Biological Fluids

  • Analytes: Creatinine, bilirubin, electrolytes (solutes).
  • Solvent: Plasma or serum.

Percent Solution Table

  1. Solid solute + solid solvent

    • Expressed in grams (G)
    • Type: Weight per weight (W/W)

  2. Solid solute + liquid solvent

    • Solute: grams
    • Solvent: milliliters (mL)
    • Type: Weight per volume (W/V)

  3. Liquid solute + liquid solvent

    • Solute: milliliters (mL)
    • Solvent: milliliters (mL)
    • Type: Volume per volume (V/V)

Key Takeaways

  • Solid solute and solvent: expressed in grams.

  • Liquid solute and solvent: expressed in milliliters (mL).

  • Formula for percent solution:

    Percent Solution = (Amount of Solute / Amount of Solution) x 100

  • Amount of solution = solute + solvent.

  • 100 is a constant in the formula.

Considerations in Calculation

  • When mixing liquid solute and solvent:
    • Volume of solution = Volume of solute + Volume of solvent
  • For solid solute: grams not added to total volume.

Sample Calculation

  1. Problem: 25 mL of concentrated alcohol diluted with 250 mL water.
    • Given: 25 mL alcohol (solute), 250 mL water (solvent).
    • Calculation:
      • Total volume = 25 mL + 250 mL = 275 mL.
      • Percent solution = (25 mL / 275 mL) x 100
      • Final Answer: 9.09% concentration of alcohol.