Concentration

Solution Concentration Concentration = quantity of solute quantity of solution There are 3 basic ways to express concentration: 1) Percentages 2) Ppm and ppb (used for very low concentration) 3) Molar concentrations

1. Percent Concentration O % concentration can be in O % Volume/Volume O % Weight/Weight O % Weight/Volume

Percent V/V Concentration % V/V = volume of solute (mL or L) x 100% volume of solution (mL or L) Example:: 140 mL of acetic acid is present in 500. mL of water. What is the percentage by volume concentration of acetic acid?

Percent W/W Concentration % W/W = weight of solute (g or Kg) x 100% weight of solution (g or Kg) Example: What is the % W/W if 8.0 g copper is added to enough zinc to produce 100. g of an alloy?

Percent W/V Concentration % W/V = weight of solute (g) x 100% volume of solution (mL) Can use g/mL or Kg/L Example: If 250 g of sodium chloride is present in 3.0 L of solution, what I the percentage weight by volume of sodium chloride?

2. Very Low Concentrations O Expressed in parts per million (ppm) or part per billion (ppb) O A type of W/W or W/V concentration O Chlorine concentration in a swimming pool may be expressed as ppm 1 mg/L or 1 mg/Kg = 1ppm 1 mg /1000 L or 1 mg/1000 Kg = 1ppb Example: 1) Convert 45 ppm to g/L, 45 ppb to g/L. 2) Convert 3.75 mg in 50 mL to ppm.

Molar Concentration Molar Concentration = amount of solute (in moles) volume of solution (in L) C = n/V Units are mol/L or M or Molar

Molar Concentration Examples: 1) If a reaction produced mol of sodium hydroxide in L of solution, calculate the molar concentration of sodium hydroxide. 2) 64 g of oxygen gas (O 2 ) are dissolved in 100. L of air. What is the concentration?