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Dilutions

Dilutions. Stock Solutions. Different experiments require solutions of various different molarities. It would not be practical to have multiple bottles of each type of solution for each different molarity needed.

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Dilutions

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  1. Dilutions

  2. Stock Solutions • Different experiments require solutions of various different molarities. • It would not be practical to have multiple bottles of each type of solution for each different molarity needed. • Concentrated (lots of moles per volume) stock solutions are stored for use in experiments. These solutions are diluted to the desired concentration as needed.

  3. Dilution • Dilution: The process of adding more solvent to a solution • Our aqueous solution are diluted by adding more water IMPORTANT: ***Only more water is added during a dilution!!! The amount of solute (number of moles) stays the same! *** Amount(moles) = same Volume(Liters) = changes

  4. Dilution—decrease in concentration Stays the SAME! M = moles of solute volume (L) DECREASES INCREASES (We’re adding water!)

  5. Dilution Example • How would you prepare 0.500L of 1.00M acetic acid from a 17.5M stock solution? • How many moles of acetic acid are required? 0.500 L solution x 1.00 mol HC2H3O2 = 0.500 mol HC2H3O2 L solution • What volume of the stock solution contains 0.500 moles of HC2H3O2? V x 17.5 mol HC2H3O2 = 0.500 mol HC2H3O2 L solution V = 0.0286 L = 28.6mL of stock solution diluted to 500mL Don’t forget! M = mol ! L

  6. 28.6 mL Add WATER to 500 mL mark 17.5M HC2H3O2 500mL 500mL 500mL 28.6 mL 1.00M HC2H3O2

  7. Let’s make those calculations easier… • Since the number of moles stays the same, we can simply write: M1 X V1 = moles of solute = M2 X V2 M1 X V1 = M2 X V2

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