Calculations involving percentage solutions

1. Percentage Solutions:

• These are solutions where the concentration of a solute in a solution is expressed as a percentage.
• In pharmacy, this typically refers to:
  • Weight/Volume (w/v)
  • Weight/Weight (w/w)
  • Volume/Volume (v/v) percentages.

2. Weight/Volume Percentage (w/v):

• Used for: Solid substances dissolved in a liquid.
• Definition: Expressed as grams of solute per 100 mL of solution.
• Calculation: 
• $\text{Weight/Volume Percentage (w/v)} = \left( \frac{\text{Weight of Solute (g)}}{\text{Volume of Solution (mL)}} \right) \times 100$
• Example:
  • If 5 grams of a drug are dissolved in 250 mL of solution, the concentration is:
  • $\left( \frac{5 \,\text{g}}{250 \,\text{mL}} \right) \times 100 = 2% \, w/v$

3. Weight/Weight Percentage (w/w):

• Used for: Mixtures of two solid substances.
• Definition: Expressed as grams of solute per 100 grams of the total solution.
• Calculation: 

4. Volume/Volume Percentage (v/v):

• Used for: Solutions where both solute and solvent are liquids.
• Definition: Expressed as milliliters of solute per 100 mL of solution.
• Calculation: 
• $\text{Volume/Volume Percentage (v/v)} = \left( \frac{\text{Volume of Solute (mL)}}{\text{Total Volume of Solution (mL)}} \right) \times 100$

This organized layout clearly separates the different types of percentage solutions with corresponding explanations, formulas, and examples.

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