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Solution Concentration

Solution Concentration. A measure of how much solute is dissolved in a specific amount of solvent or solution. Described qualitatively using “dilute” and “concentrated” Can be calculated quantitatively by mass ( molarity ) or by volume ( molality )

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Solution Concentration

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  1. Solution Concentration • A measure of how much solute is dissolved in a specific amount of solvent or solution. • Described qualitatively using “dilute” and “concentrated” • Can be calculated quantitatively by mass (molarity) or by volume (molality) • Can also be expressed as a percent – either percent by mass or percent by volume

  2. Solution Concentration • If the solute is a solid being dissolved in a liquid, usually use molarity or % by mass • If the solute is a liquid being dissolved in a liquid, usually use molality or % by volume

  3. Percent Concentration • Percents are a ratio of the amount of solute over the total amount of solution times 100% • The amount can be measured in mass or volume but both measurements must be the same unit

  4. Try It • A salt water aquarium must maintain a sodium chloride solution similar to ocean water which is 3.6 g NaCl per 100.0 g of water. What is the % by mass of NaCl in the solution? 3.6 / (3.6 + 100.0) X 100% = 3.5%

  5. Try It • Isopropyl rubbing alochol is usually 70% alcohol and 30% water. If you have 750 ml of rubbing alcohol, how much is isopropyl alcohol and how much is water? .70 x 750 ml = 525 ml of alcohol .30 x 750 ml = 225 ml of water

  6. Molarity • One of the most common ways to describe concentration quantitatively • Also called molar concentration • Abbreviated with a capital M (yes, just like Molar Mass) • Calculated by dividing the moles of solute by the liters of solution • Label is moles per liter or M

  7. Try It • You have a 100 ml sample of an aqueous solution that contains .085 moles of KCl. What is it’s molarity? 100 ml x 1l / 1000 ml = .100 L .085 molKCl / .100 L = .85 mol/L or .85M

  8. Preparing a Molar Solution • How many grams of sucrose (C12H22O11) is needed to prepare one liter of a 1.50 M solution? • You’ll need the molar mass of sucrose: 1.5 mol 342 g _____________ X ___________ = 513 g / liter 1 liter 1 mol

  9. Preparing a Molar Solution • How many grams of sucrose (C12H22O11) is needed to prepare 100 mL of a 1.50 M solution? 1.5 mol 342 g _____________ X ___________ = 513 g / liter 1 liter 1 mol 1 L 513 g 100 mL X __________ X _____________ = 51.3 g 1000 mL 1 L

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