2 CALCULATING CONCENTRATION OF SOLUTIONS 1. Mass Percent = (mass of solute/mass of solution)1002. Parts per million = (mass of solute/mass of solution)1063. Mass/volume percent = (mass of solute/mL solution)1004. Volume percent = (mL solute / mL solution)1005. Molarity = n/V = moles solute / L solution6. Molality = moles of solute / kg solvent
3 CALCULATING CONCENTRATION OF SOLUTIONS What is the mass percent of a solution made by adding 25.0 g of KCl to mL of water?What is the concentration of a solution made by mixing 25.0 g of KCl in (a) mL and (b) L of water in ppm?
4 The following slides are extra worked out examples.
5 CALCULATING CONCENTRATION OF SOLUTIONS How many grams of a solution that is 32.7% by mass NaCl would contain 45.0 g of NaCl?Mass % = (mass of solute /mass of solution) 10032.7 % = (45.0 g / x )100x = 45.0 g / 0.327x = mass of solution = 138 g
6 CALCULATING CONCENTRATION OF SOLUTIONS How much solute is present in mL of a 14.7% (mass/volume) HCl solution?Mass/volume % = (masssolute/volumesolution) 10014.7 % = (x / mL )100x = (756.1 mL)x = mass of solute = 111g
7 CALCULATING CONCENTRATION OF SOLUTIONS How many grams of LiF are in 500 mL of a solution that is 18.4% by mass and has a density of g/mL?Masssolution = densitysolution (Volumesolution)= g/mL (500 mL)= g solutionMass% = (masssolute/masssolution) 10018.4 % = (x / g )100x = (598.5 g)x = mass of solute = 110 g
8 CALCULATING CONCENTRATION OF SOLUTIONS A 350 mL sample of drinking water was analyzed and found to contain g of sulfate salts. Calculate the concentration of sulfate salts in this water sample?Masswater = densitywater (Volumewater)= 1.00 g/mL (350 mL)= 350 g solutionppm = (masssolute/masssolution) 106ppm = (0.0046g / 350 g ) 106ppm = 13 ppmUse ppm for trace amounts of solute.
9 CALCULATING CONCENTRATION OF SOLUTIONS Calculate the molality of a solution composed of 53.0 g of KOH in 500 mL of water.First calculate the moles of solute:n = 53.0 g (1 mol / 56 g) = mol soluteNext, m = moles of solute / kg solventm = (0.946 mol / kg )m = 1.89 molal solution
10 PRACTICE PROBLEMS #36 calculating the CONCENTRATION OF SOLUTIONS ___1. How many grams of a 45.0 % Mg(OH)2 solution can be made from 7.00 g of solid Mg(OH)2?___2. How many kilograms of a 6.8% KC2H3O2 solution will contain 5.3 moles of KC2H3O2?___3. How many grams of KOH are needed to make mL of a solution that is to contain 6.70 mg/mL of potassium ion?___4. If g of a 25.0 % sucrose solution was prepared, how many grams of a 5.00% solution of sucrose would contain the same amount of sugar?___5. How many grams of solution, 10.0% KOH by mass, are required to neutralize 25.0 mL of a 2.00 M HCl solution if the moles of HCl is equal to the moles of KOH?15.6 g7.6 kg2.41 g673 g28.0 g
11 Group study problem #36 calculating the CONCENTRATION OF SOLUTIONS ___1 How many grams of a solution, that is 76.3% by mass KBr, would contain g of KBr?___2. What is the ppm and molality of a solution containing 75.0 g of ethylene glycol, C2H6O2, in g of water?___3. How many grams of CuSO4 are needed to make mL of a solution that contains 10.5 mg/mL of Cu2+ ion? Calculate the molarity of the resulting solution.___4. Automobile battery acid is 38% H2SO4 and has a density of 1.29 g/mL. Calculate the molality of this solution.___5. If 27.0 g of LiBr are dissolved in 50.0 g of water, the percent of LiBr by mass is___6. If 15.0 g of KNO3 is added to 75g of water, what is the mass percent of KNO3 in the solution?