Solution Concentration. Solution Concentration. Concentration : the quantity of a given solute in solution Dilute : having a relatively small quantity of solute per unit volume of solution Concentrated : having a relatively large quantity of solute per unit volume of solution.
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Solution Concentration Concentration: the quantity of a given solute in solution Dilute: having a relatively small quantity of solute per unit volume of solution Concentrated: having a relatively large quantity of solute per unit volume of solution
In general, the concentration, “c” (lower case letter c), of any solution is expressed by the ratio quantity of solute Concentration = quantity of solvent
Amount Concentration • A chemists way of expressing solution concentration in terms of the amount (in moles) of solute per litre of solution • Traditionally, called molar concentration or molarity, used the symbol “M” • According to IUPAC, these terms are no longer correct and have been replaced with “amount concentration”
Amount Concentration • The amount concentration, c, of a solution is determined by dividing the amount (in moles) of solute, n, by the volume (in litres) of the solution, V: amountof solute (in mol) amount = concentration volume of solution (in L)
Weight/Volume Percent • percent (w/v) or percent (m/v) • Used with one solid and one liquid • Often used when describing unsaturated solutions mass of solute (in g) weight/volume = percent X 100% volume of solution (in mL) Example: Intravenous fluid is 0.9% (w/v) NaCl = 0.9 g of NaCl dissolved in 100 mL of solution
Weight/Weight Percent • weight percent, mass percent, percent (w/w) or percent (m/m) • Used with two solids or solutions of a solid dissolved in a liquid • Useful when dealing with alloys of precious metals mass of solute (in g) weight/weight = percent X 100% mass of solution (in g)
Weight/Weight Percent Example: The concentration of Mg2+ in seawater is 0.129% (w/w) = 0.129 g of Mg2+ dissolved in 100 g of seawater
Parts Per Million, Billion, and Trillion Environmental solutions are often very low concentration. Convenient to express concentrations in terms of parts per million (ppm) or parts per billion (ppb).
Both parts per million and parts per billion are fractions, with the mass of the solute divided by the mass of the solution ppm = mass of solute x 106 mass of solution ppb = mass of solute x 109 mass of solution
Calculating Concentration in ppm Health Canada’s guideline for the maximum mercury content in commercial fish is 0.5 ppm. When a 1.6 kg salmon was tested, it was found to contain 0.6 mg of mercury. Would this salmon be safe to eat?
ppm = mass of solute x 106 mass of solution Substitute given data. Express BOTH masses in grams allowing cancellation. ppm = 0.6 mg x 106 = 6 x 10-4 g x 106 1.6 kg 1.6x 103 g = 0.4 ppm Less than minimum guideline, therefore salmon is safe to eat.