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Published byCecily Wilkins Modified over 8 years ago

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**Molarity = Molarity ( M ) moles solute liters of solution**

Molarity is defined as the amount of moles of a compound dissolved in an amount of solvent (usually water). It can be solved with the equation: Molarity ( M ) = moles solute liters of solution

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**Molarity – What is it? A measure of how concentrated a solution is.**

Think about making Kool-Aid. What makes Kool-Aid more delicious? The more sugar you add, the sweeter the solution gets. Adding more moles of sugar, without changing the volume makes the Molarity “Concentration” Increase

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Molarity Practice 1) 80.5 grams of sodium chloride is dissolved in 3.5 Liters. Determine the Molarity. 2) 125 grams of Calcium Fluoride is dissolved in 250 mL of water. Solve for the Molarity.

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**2.80 M = x mol / 0.500 L = 1.40 mol 1.40 mol 166 g KI 1 mol KI**

What mass of KI is required to make 500. mL of a 2.80 M KI solution? 2.80 M = x mol / L = 1.40 mol 1.40 mol 166 g KI 1 mol KI = 232 g KI 12.3

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Dilution of Solutions Dilution is the procedure for preparing a less concentrated solution from a more concentrated solution. When you want to dilute a solution, what happens to the number of moles present in the solution? Do they increase? Decrease? Stay the same? Stay the same. 5

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Since moles are constant before and after dilution, we can use the following formula for dilution calculations. M1V1=M2V2 M1 = Starting Molarity , V1 = Initial Volume of solution M2 = Final Molarity, V2 = Final Volume of solution

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Example Describe how you would prepare 800mL of a 2.0M H2SO4 solution, starting with a 6.0 M stock solution. MiVi = MfVf 6.0M x Vi = 2.0M x 0.800L Vi = 1.6M x L/ 6.0M Vi = 0.26L How much water will need to be added?

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**How would you prepare 60.0 mL of 0.2 M **

HNO3 from a stock solution of 4.00 M HNO3? MiVi = MfVf Mi = 4.00 Mf = 0.200 Vf = 0.06 L Vi = ? L Vi = MfVf Mi = 0.200 x 0.06 4.00 = L = 3 mL 3 mL of acid + 57 mL of water = 60 mL of solution 4.5

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**Solution Stoichiometry**

We use the same ideas when we converted from grams of one compound to grams of another, except we are in mL of solution instead of grams. Use the Molarity equation: M = mol/L Use stoichiometry to convert moles of one compound to moles of the other compound. X grams X mol X grams Y mol X mol Y grams Y mol

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**Solution Stoich Practice**

How many mL of 2.00 M Hydrobromic acid, when reacted with aluminum hydroxide, will be required to produce 60.0 grams of water in the acid base reaction? ___HBr +___Al(OH)3 ___H2O + ___ AlBr3 3 1 3 1 60.0 g H2O 1 mol H2O g H2O 3 mol HBr 3 mol H2O = 3.33 mol HBr 3.33 mol HBr 2.00 M HBr = = 1.67 mL HBr X ml HBr

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