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II III I II. Solution Concentration (p. 480 – 486) Ch. 16 – Solutions

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A. Concentration The amount of solute in a solution Describing Concentration % by mass - medicated creams % by volume - rubbing alcohol ppm, ppb - water contaminants molarity - used by chemists molality - used by chemists

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B. Percent Solutions Percent By Volume (%(v/v)) Concentration of a solution when both solute and solvent are liquids often expressed as percent by volume total combined volume substance being dissolved

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B. Percent Solutions Find the percent by volume of ethanol (C 2 H 6 O) in a 250 mL solution containing 85 mL ethanol. 85 mL ethanol 250 mL solution = 34% ethanol (v/v) Solute = 85 mL ethanol Solution = 250 mL % (v/v) = x 100

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B. Percent Solutions Percent By Mass (%(m/m)) Concentration of a solution when solute is solid sometimes expressed as percent by mass total combined volume substance being dissolved

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B. Percent Solutions How much glucose should you use to make g of a 2.8% (m/m) solution in water? unknown g glucose g solution = g glucose Percent (m/m) = 2.8% Solution = g 2.8 = x 100

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C. Molarity Concentration of a solution most often used by chemists total combined volume substance being dissolved

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C. Molarity 2M HCl What does this mean?

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Molar Mass (g/mol) particles/mol MASS IN GRAMS MOLES NUMBER OF PARTICLES Molar Volume (22.4 L/mol) LITERS OF GAS AT STP LITERS OF SOLUTION Molarity (mol/L) D. Molarity Calculations

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How many moles of NaCl are required to make 0.500L of 0.25M NaCl? L soln 0.25 mol NaCl 1 L soln = mol NaCl

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D. Molarity Calculations How many grams of NaCl are required to make 0.500L of 0.25M NaCl? L soln 0.25 mol NaCl 1 L soln = 7.3 g NaCl g NaCl 1 mol NaCl

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D. Molarity Calculations Find the molarity of a 250 mL solution containing 10.0 g of NaF g NaF 1 mol NaF g NaF = 0.95 M NaF.25 L soln

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E. Dilution Preparation of a desired solution by adding water to a concentrate Moles of solute remain the same

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E. Dilution What volume of 15.8M HNO 3 is required to make 250 mL of a 6.0M solution? GIVEN: M 1 = 15.8M V 1 = ? M 2 = 6.0M V 2 = 250 mL WORK: M 1 V 1 = M 2 V 2 (15.8M) V 1 = (6.0M)(250mL) V 1 = 95 mL of 15.8M HNO 3

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F. Molality mass of solvent only 1 kg water = 1 L water

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G. Molality Calculations Find the molality of a solution containing 75 g of MgCl 2 in 250 mL of water. 75 g MgCl 2 1 mol MgCl g MgCl 2 = 3.2 m MgCl kg water

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G. Molality Calculations How many grams of NaCl are reqd to make a 1.54m solution using kg of water? kg water1.54 mol NaCl 1 kg water = 45.0 g NaCl g NaCl 1 mol NaCl

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H. Preparing Solutions 500 mL of 1.54M NaCl 500 mL water 45.0 g NaCl mass 45.0 g of NaCl add water until total volume is 500 mL mass 45.0 g of NaCl add kg of water 500 mL mark 500 mL volumetric flask 1.54m NaCl in kg of water

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H. Preparing Solutions Copyright © NT Curriculum Project, UW-Madison (above: Filling the volumetric flask)

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H. Preparing Solutions Copyright © NT Curriculum Project, UW-Madison (above: Using your hand as a stopper)

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H. Preparing Solutions 250 mL of 6.0M HNO 3 by dilution measure 95 mL of 15.8M HNO 3 95 mL of 15.8M HNO 3 water for safety 250 mL mark combine with water until total volume is 250 mL Safety: Do as you oughtta, add the acid to the watta! or AA – add acid!

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Solution Preparation Mini-Lab Turn in one paper per team. Complete the following steps: A) Show the necessary calculations. B) Write out directions for preparing the solution. C) Prepare the solution. For each of the following solutions: 1) mL of 0.50M NaCl 2) 0.25m NaCl in mL of water 3) mL of 3.0M HCl from 12.0M concentrate. (dont actually prepare this one!)

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