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Concentration of Solutions

Concentration of Solutions. Concentration. A measurement that describes how much solute is in a given amount of solvent or solution. Many, many different units to express concentration. Pick the unit by the task at hand. Percent. By mass By Volume Part over Whole times 100%. Twists.

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Concentration of Solutions

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  1. Concentration of Solutions

  2. Concentration • A measurement that describes how much solute is in a given amount of solvent or solution. • Many, many different units to express concentration. Pick the unit by the task at hand.

  3. Percent • By mass • By Volume • Part over Whole times 100%.

  4. Twists • Sometimes they ask for the part or the whole, not the percent. • Sometimes they give you the volume/mass of the solution; sometimes they give you the volume/mass of the solvent and the volume/mass of the solute. • Mass solution = Mass solute + Mass solvent

  5. Molarity (M) Molarity (M) = moles of solute liters of solution Movie on Preparing Solutions

  6. Recall the mole map! # of grams  by F.M. X F.M. # of moles

  7. Twists • Sometimes they give moles of solute; sometimes they give grams of solute. Gramsmust beconverted to moles. • Sometimes they give mL of solution instead of Liters. Millilitersmust beconverted to liters. • Sometimes they ask for the grams or moles of solute or the volume, rather than the molarity.

  8. Rearranging … Molarity (M) = # moles of solute liters of solution Liters of solution = # of moles solute Molarity # of moles of solute = Molarity X Liters

  9. PPM (parts per million) • PPM = grams solute X 1,000,000 • Usually used when the solute is present in very small amounts. • (The Regents don’t follow this rule.) grams solution

  10. PPM (parts per million) • PPM = grams solute X 1,000,000 • PPM is a ratio between the mass of the solute & the mass of the solution. • Kind of like % except you multiply by 1,000,000 instead of 100. grams solution

  11. About 0.0043 g of O2 can be dissolved in 100 mL of water at 20oC. Express in ppm. • Remember 1 mL of water has a mass of 1 g. • PPM = (0.0043g / 100.0043) X 1,000,000. • PPM = 43 ppm

  12. CO2 gas has a solubility of 0.0972 g/100 g water at 40oC. Express in parts per million. PPM = (0.0972 g / 100.0972 g solution) X 1,000,000. PPM = 971 ppm.

  13. What is the concentration in ppm of a solution with 30.0 g NaNO3 in 70.0 g water? PPM = (30.0 g NaNO3 / 100.0 g solution) X 1,000,000. PPM = 300,000 = 3.0 X 105

  14. How many grams of KOH are needed to be dissolved in water to make 2000.0 grams of a 10.0 ppm solution? 10 ppm = (? grams KOH / 2000.0 g solution) X 1,000,000. Divide both sides by 1,000,000. 1 X 10-5 ppm = (? grams KOH / 2000.0 g soln.) Multiply both sides by 2000. 0.02 = grams KOH

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