Aqueous Reactions and Solution Stoichiometry CDO High School

Solute: the substance that is dissolved in another substance Solute and solvent Solute: the substance that is dissolved in another substance Solvent: the substance that something is dissolved into it

Concentrated vs Dilute Concentration: refers to how much solute is dissolved in the solvent Concentrated: solutions with a large amount of solute dissolved in solvent Dilute: solutions with a small amount of solute dissolved the solvent

volume of solution in liters Molarity Two solutions can contain the same compounds but be quite different because the proportions of those compounds are different. Molarity is one way to measure the concentration of a solution. moles of solute volume of solution in liters Molarity (M) =

Units of Molarity 2.0 M HCl = 2.0 moles HCl 1 L HCl solution 6.0 M HCl = 6.0 moles HCl LecturePLUS Timberlake

Molarity Calculation NaOH is used to remove potato peels commercially. If 4.0 g NaOH are used to make 500. mL of NaOH solution, what is the molarity (M) of the solution? LecturePLUS Timberlake

Calculating Molarity 1) 4.0 g NaOH ÷ 40.0 g/mol NaOH = 0.10 mole NaOH 2) 500. mL x 1 L _ = 0.500 L 1000 mL 3) 0.10 mole NaOH = 0.20 mole NaOH = 0.20 M NaOH 0.500 L 1 L LecturePLUS Timberlake

Learning Check M1 A KOH solution with a volume of 400 mL contains 2 mole KOH. What is the molarity of the solution? Drano LecturePLUS Timberlake

Learning Check M2 A glucose solution with a volume of 2.0 L contains 72 g glucose (C6H12O6). If glucose has a molar mass of 180. g/mole, what is the molarity of the glucose solution? LecturePLUS Timberlake

Learning Check M3 Stomach acid is a 0.10 M HCl solution. How many moles of HCl are in 1500 mL of stomach acid solution? LecturePLUS Timberlake

Learning Check M4 How many grams of KCl are present in 2.5 L of 0.50 M KCl? LecturePLUS Timberlake

Solution M4 3) 2.5 L x 0.50 mole x 74.6 g KCl = 93 g KCl 1 L 1 mole KCl LecturePLUS Timberlake

Learning Check M5 How many milliliters of stomach acid, which is 0.10 M HCl, contain 0.15 mole HCl? LecturePLUS Timberlake

Learning Check M6 How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution? LecturePLUS Timberlake

Solution Stoichiometry The majority of work in research and industry involves solutions. Recall that solutions are easy to handle and are usually easier to control in reactions. Solution stoichiometry – the procedure for calculating the molar concentration or volume of solution products or reactants

Mass A (g) Volume Volume A B (L) (L) Mole Mole A B (mol) (mol) ÷ Molarity A ÷ Molar Mass X Molar Mass ÷ Molarity B X Molarity A X Mole Ratio X Molarity B Mole A (mol) Mole B (mol) X Mole Ratio ÷ Volume B ÷ Volume A Molarity A (M) Molarity B (M) X Volume B X Volume A X Molar Mass ÷ Molar Mass Mass B (g)

Example #1 Ammonia and phosphoric acid solutions are used to produce ammonium hydrogen phosphate fertilizer. What volume of 14.8 M NH3(aq) is needed to react with 1000 L of 12.9 M of H3PO4(aq)? 2NH3(aq) + H3PO4(aq)  (NH4)2HPO4(aq) 1000 L x 12.9 mol x 2mol ÷ 14.8 mol/L = 1740 L 1 L 1mol

Example #2 In an experiment, .01000 L sample of sulfuric acid solution reacts completely with 0.0159 L of 0.150 M potassium hydroxide. Calculate the concentration of the sulfuric acid. H2SO4(aq) + 2KOH(aq)  2H2O(l) + K2SO4(aq) 0.0159 L x 0.150 mol x 1mol x 1 = 0.119 mol/L 1 L 2 mol 0.0100 L

2 AgNO3(aq) + K2CrO4(aq)  Ag2CrO4(s) + 2 KNO3(aq) Example #3 How many grams of silver chromate will form when 120 mL of 0.500 M silver nitrate are added to potassium chromate? 2 AgNO3(aq) + K2CrO4(aq)  Ag2CrO4(s) + 2 KNO3(aq)

Pb(NO3)2(aq) + 2MgCl2(aq)  PbCl2(s) + Mg(NO3)2(aq) Example #4 If you mix 200 ml of 0.100 M Pb(NO3)2 and 300 ml of 0.200 M MgCl2, how much PbCl2 precipitate will you form? Pb(NO3)2(aq) + 2MgCl2(aq)  PbCl2(s) + Mg(NO3)2(aq)

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