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Concentration of solutions CONCENTRATED = Lots of solute in the solution DILUTE = Not much solute in the solution

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Ways to express concentration numerically Molarity % by Mass % by Volume Parts per million

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MOLARITY

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Molarity = # of moles of solute in 1 liter of solution

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See Table T

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Molarity Problems What is the molarity of a solution of NaOH if there are 4 moles of NaOH dissolved water to make 1 liter of solution? 4 moles = 4 M 1 liter

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Molarity Problems What is the molarity of a solution of NaOH if there are 4 moles of NaOH dissolved water to make 2 liters of solution? 4 moles = 2 M 2 liter

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Molarity Problems What is the molarity of a solution of NaOH if there are 2 moles of NaOH dissolved water to make 6 liters of solution? 2 moles =.33 M 6 liters

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Molarity Problems What is the molarity of a solution of NaOH if there are 2 moles of NaOH dissolved water to make.5 liters of solution? 2 moles = 4 M.5 liters

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Molarity Problems What is the molarity of a solution of NaOH if there are 40 grams of NaOH dissolved water to make 1 liters of solution? First, convert grams to moles: Na = 23 g/mol O = 16 g/mol so 40 g = 1 mole H = 1 g/mol 40 g/mole GFM

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Molarity Problems What is the molarity of a solution of NaOH if there are 40 grams of NaOH dissolved water to make 1 liters of solution? 1 moles = 1 M 1 liters

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Molarity Problems What is the molarity of a solution of NaOH if there are 80 grams of NaOH dissolved water to make 1 liters of solution? 80g/40g/mol = 2 moles 2 moles = 2 M 1 liters

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Molarity Problems What is the molarity of a solution of NaOH if there are 3.6 grams of NaOH dissolved water to make 2 liters of solution? 3.6g/40g/mole = 0.09 moles 0.09 moles = 0.045 M 2 liters

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In General…. Concentrations < 1M are considered weak, or dilute Concentrations > 1M are considered strong, or concentrated Always know the concentration of your solution before you use it!!!! (read the label)

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Can you…. Rearrange the molarity equation to solve for moles? Molarity = Moles Liter moles = ?

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Can you…. Rearrange the molarity equation to solve for moles? Molarity = Moles Liter moles = Liter x Molarity

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Can you…. Rearrange the molarity equation to solve for Liters? Molarity = Moles Liter Liters = ?

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Can you…. Rearrange the molarity equation to solve for Liters? Molarity = Moles Liter Liters = Moles Molarity

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Example How many moles of NaOH do you have if you have 3 liters of a 0.5M NaOH solution? Moles = Molarity x Liters Moles = 0.5M x 3 liters Moles = 1.5

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% Mass Uses the same formula as % composition (See Table T) Percent mass = mass of part x 100 Mass of whole

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% Mass What is the % mass of NaOH if 2.5 g of NaOH are added to 50 g of water? Percent mass = mass of part (solute) x 100 Mass of whole (solution) % mass = 2.5g x 100 (2.5 + 50g) % mass = (2.5 / 52.5) x 100 = 4.76% solution

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% Volume Uses the same formula as % composition (See Table T) Percent volume = volume of part x 100 volume of whole

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% Volume What is the % volume of NaOH if 20 ml of NaOH are added to 300 ml of water? Percent volume = volume of part (solute) x 100 volume of whole (solution) % volume = 20 ml x 100 (20 ml + 300 ml) % volume = (20 / 320) x 100 = 6.25% solution

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Parts per million ppm = grams solute x 1,000,000 grams solution This is used when the amount of solute is very very small

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Parts per million ppm = grams solute x 1,000,000 grams solution.0043 g of oxygen gas dissolve in 100 ml of water at 20 degrees celsius. What is the concentration in ppm?

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Parts per million ppm =.0043g x 1,000,000 (100 g + 0.0043g) Concentration = 43 ppm

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