# Section 4.5 Concentrations of Solutions. Concentration Amount of solute dissolved in a given quantity of solvent or solution Amount of solute = Concentration.

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Section 4.5 Concentrations of Solutions

Concentration Amount of solute dissolved in a given quantity of solvent or solution Amount of solute = Concentration

Molarity (M) Concentration of a solution moles of solute volume of solution in liters Molarity (M) =

SAMPLE EXERCISE 4.11 Calculating Molarity Calculate the molarity of a solution made by dissolving 23.4 g of sodium sulfate (Na 2 SO 4 ) in enough water to form 125 mL of solution. Solve: The number of moles of Na 2 SO 4 is obtained by using its molar mass: Converting the volume of the solution to liters:

Concentration of Electrolytes For ionic compounds: Look at chemical formula for relative concentration of ions Ex 1: 1.0M NaCl is 1.0M Na + and 1.0M Cl - Ex 2: 1.0M Na 2 SO 4 is 2.0 M Na + and 1.0M SO 4 2-

Dilution Process of lowering the concentration of a solution by adding water

Dilution Problem We want: 250.0 mL of 0.100 M CuSO 4 We have: 1.00M CuSO 4 Moles solute before dilution = Moles after Mol CuSO 4 in dil soln = 0.250L soln x 0.100mol CuSO 4 L soln = 0.0250 mol CuSO 4 Liters of conc soln = (0.0250 mol CuSO 4 ) x 1 L soln 1.00mol CuSO 4 = 0.0250 L Pipet 0.0250L conc sol add dilute it to 250.0 mL

Quick Calculation M conc x V conc = M dil x V dil Why can we ignore moles in dilution problems?

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