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Concentration Units

Concentration Units. Percent by mass, mole fraction, molarity, and molality. Percent by mASS. PERCENT BY MASS =. MASS OF SOLUTE. X 100%. MASS OF SOLUTION. A sample of 0.892g of potassium chloride is dissolved in 54.6g of water. What is percent by mass of KCl in the solution?.

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Concentration Units

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  1. Concentration Units Percent by mass, mole fraction, molarity, and molality

  2. Percent by mASS PERCENT BY MASS = MASS OF SOLUTE X 100% MASS OF SOLUTION A sample of 0.892g of potassium chloride is dissolved in 54.6g of water. What is percent by mass of KCl in the solution? 0.892g Percent by mass of KCl = X 100% 0.892g + 54.6g = 1.61%

  3. Concentration Units Percent by mass, mole fraction, molarity, and molality

  4. Mole fraction (x) MOLE FRACTION OF COMPONENT A = XA = Moles of A Σ all moles in solution Your solution contains 5 moles of KCl and 15 moles of water. What is the mole fraction of KCl? 5 moles KCl XKCl = = 0.25 5 moles KCl + 15 moles H2O What is the mass percent of KCl? 74.55 g 5 molKCl x Mass percent of KCl = 1 molKCl = 58% 74.55 g 18.02 g 15 mol H2O x 5 molKCl x + 1 molKCl 1 mol H2O

  5. Concentration Units Percent by mass, mole fraction, molarity, and molality

  6. Molarity and molality Moles of solute Moles of solute MOLALITY = m = MOLARITY = M = Kg of solvent Liters of solution Calculate the molality of a sulfuric acid solution containing 24.4g of sulfuric acid in 198g of water. The molar mass of sulfuric acid is 98.09 g/mol. 1 mol H2SO4 24.4 g H2SO4 x mH2SO4 = 98.09 g = 1.26m = 1.26 “molal” 0.198 kg H2O What is the molarity of the solution? (d = 1.84 g/mL) 1 mL = 120.87 mL Volume of solution = (24.4g + 198g) 1.84g 0.2487 mol H2SO4 Molarity = M = = 2.06M = 2.06 “molar” 0.12087L solution

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