Report

Solution Concentrations Percent by Mass (m/m) Mass of solute ×100 Mass of solution Solution = solute + solvent Example 1 An aquarium must contain 13.6 g NaCl per 100.0 g of water. What is the percent by mass (m/m) of NaCl in the solution? Solute:13.6g (smaller #) + Solvent: 100.0g (larger #) Solution: 113.6g 13.6 ×100 = 11.97% ≈ 12.0% 113.6 Example 2 You have a 650.0g KCL solution. If the percent by mass is 1.25% (m/m), how many grams of solute is in the solution? How many grams of solvent are in the solution? Solution: 650.0g − Solute: 8.13g Solvent = 641.87g ≈ 642g solute ×100 = 1.25% 650.0 Solute = 8.13g Percent by Volume (v/v) Volume of solute ×100 Volume of solution Solution = solute + solvent Example 1 What is the percent by volume of ethanol in a solution that contains 45mL of ethanol dissolved in 145mL of water? Solute: 45mL (smaller #) + Solvent: 145mL (larger #) Solution: 190mL 45 190 ×100 = 23.68% ≈ 24% Example 2 If you have 200.0 mL of a 35.0% aqueous solution of ethanol, what volume of ethanol and water are in the solution? Solution: 200.0mL − Solute: 70.0mL Solvent = 130.0mL ≈ 130. or 1.3×102 mL solute ×100 = 35.0% 200.0 Solute = 70.0mL Parts Per Million (ppm) Solute ×106 Solution 1 ppm = 1mg/L Example 1 If 25 grams of a chemical is dissolved in 75 grams of water, what is the concentration of the chemical in parts per million (ppm)? Solute: 25g (smaller #) + Solvent: 75g (larger #) Solution: 100g 25 100 ×106 = 250,000 or 2.5×105 g Example 2 Suppose 17 grams of sucrose is dissolved in 183 grams of water. What is the concentration of sucrose in ppm? Solute: 17g (smaller #) + Solvent: 183g (larger #) Solution: 200g 17 200 ×106 = 85,000 or 8.5×104 g Example 3 150 mL of an aqueous sodium chloride solution contains 0.0045g NaCl. Calculate the concentration of NaCl in parts per million (ppm). Remember 1ppm = 1 mg/L 0.0045g 150mL 1000mg 1g 1000mL 1L = 30 mg/L = 30 ppm Example 4 Convert 0.0035% NaCl by mass into parts per million of NaCl. * Think of 0.0035% like your grade on a test; 0.0035% means 0.0035 out of 100 0.0035 ×106 = 35ppm 100