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Learn the process of making standard solutions from liquids, understand markings on glassware, and grasp concepts like molarity and molality. Solve various concentration problems with detailed explanations.
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How to mix a Standard Solution Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 480
Process of Making a Standard Solution from Liquids Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 483
Markings on Glassware Beaker 500 mL + 5% Range = 500 mL + 25 mL 475 – 525 mL Graduated Cylinder 500 mL + 0.2 mL Range = 499.8 – 500.2 mL Volumetric Flask TC 20oC “to contain at a temperature of 20 oC” 22 T TD “to deliver” “time in seconds” s
Concentration…a measure of solute-to-solvent ratio concentrateddilute “lots of solute” “not much solute” “watery” Add water to dilute a solution; boil water off to concentrate it.
mol D. molality (m) = moles of solute M L kg of solvent A. mass % = mass of solute mass of sol’n B. parts per million (ppm) also, ppb and ppt -- commonly used for minerals or contaminants in water supplies C. molarity (M) = moles of solute L of sol’n -- used most often in this class
WRONG 7.85 kg KCl are dissolved in 2.38 L of solution. Find molality. 24.8 g table sugar (i.e., sucrose, C12H22O11) are mixed into 450 g water. Find molality.
What mass of CaF2 must be added to 1,000 L of water so that fluoride atoms are present at a conc. of 1.5 ppm? = 3.34 x 1028 m’cules H2O
mol M L How many moles solute are required to make 1.35 L of 2.50 M solution? mol = M L = 2.50 M (1.35 L) = 3.38 mol A. What mass sodium hydroxide is this? B. What mass magnesium phosphate is this?
Find molarity if 58.6 g barium hydroxide are in 5.65 L solution.
You have 10.8 g potassium nitrate. How many mL of solution will make this a 0.14 M solution? convert to mL
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
mass of solvent only 1 kg water = 1 L water Molality
Molarity of Solutions Molarity of Solutions Molarity of Solutions http://www.unit5.org/christjs/tempT27dFields-Jeff/Solutions1.htm