2 A. Concentration The amount of solute in a solution Describing Concentration% by mass - medicated creams% by volume - rubbing alcoholppm, ppb - water contaminantsmolarity - used by chemistsmolality - used by chemists
3 SAWS Water Quality Report - June 2000 A. ConcentrationSAWS Water Quality Report - June 2000
4 substance being dissolved A. MolarityConcentration of a solutionsubstance being dissolvedtotal combined volume
7 B. Molarity Calculations How many grams of NaCl are required to make 0.500L of 0.25M NaCl?0.500 L sol’n58.44 g NaCl1 mol NaCl0.25 mol NaCl1 L sol’n= 7.3 g NaCl
8 B. Molarity Calculations Find the molarity of a 250 mL solution containing 10.0 g of NaF.10.0 g NaF1 mol NaF41.99 g NaF= 0.95 M NaF.25 L sol’n
9 C. DilutionPreparation of a desired solution by adding water to a concentrate.Moles of solute remain the same.
10 C. DilutionWhat volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution?GIVEN:M1 = 15.8MV1 = ?M2 = 6.0MV2 = 250 mLWORK:M1 V1 = M2 V2(15.8M) V1 = (6.0M)(250mL)V1 = 95 mL of 15.8M HNO3
11 D. Molalitymass of solvent only1 kg water = 1 L water
12 D. MolalityFind the molality of a solution containing 75 g of MgCl2 in 250 mL of water.75 g MgCl21 mol MgCl295.21 g MgCl20.25 kg water= 3.2m MgCl2
13 D. MolalityHow many grams of NaCl are req’d to make a 1.54m solution using kg of water?0.500 kg water1.54 mol NaCl1 kg water58.44 g NaCl1 mol NaCl= 45.0 g NaCl
14 E. Preparing Solutions 1.54m NaCl in 0.500 kg of water 500 mL of 1.54M NaClmass 45.0 g of NaCladd water until total volume is 500 mLmass 45.0 g of NaCladd kg of water500 mL water45.0 g NaCl500 mLmarkvolumetricflask
17 E. Preparing Solutions 250 mL of 6.0M HNO3 by dilution measure 95 mL of 15.8M HNO395 mL of 15.8M HNO3combine with water until total volume is 250 mL250 mL markSafety: “Do as you oughtta, add the acid to the watta!” or AA – add acid!water for safety
18 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 NaCl2) 0.25m NaCl in mL of water3) mL of 3.0M HCl from 12.0M concentrate. (don’t actually prepare this one!)
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