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**Solution Concentrations**

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**Solution = solute + solvent**

Percent by Mass (m/m) Mass of solute Mass of solution ×100 Solution = solute + solvent

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**Water is always a solvent!!!**

Example 1 solute solvent An aquarium must contain 13.6 g NaCl per g of water. What is the percent by mass (m/m) of NaCl in the solution? Water is always a solvent!!! Solute:13.6g (smaller #) Solvent: 100.0g (larger #) Solution: 113.6g Mass of solute Mass of solution ×100 + 13.6 113.6 ×100 = 11.97% ≈ 12.0%

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**Example 2 − solute 650.0 ×100 = 1.25% Solute = 8.13g**

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? Then remember: solute + solvent = solution and solve for solvent First find solute: Solution: 650.0g Solute: 8.13g Solvent = g ≈ 642g solute 650.0 ×100 = 1.25% − Solute = 8.13g

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**Percent by Volume (v/v)**

Volume of solute Volume of solution ×100 Solution = solute + solvent

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Example 3 What is the percent by volume of ethanol in a solution that contains 45mL of ethanol dissolved in 145mL of water? solute solvent Then remember: solute + solvent = solution and solve for solvent Solute: 45mL (smaller #) Solvent: 145mL (larger #) Solution: 190mL 45 190 ×100 = 23.68% ≈ 24% +

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**Means dissolved in water; water is the solvent**

Example 4 If you have mL of a 35.0% aqueous solution of ethanol, what volume of ethanol and water are in the solution? First find solute: Solution: 200.0mL Solute: 70.0mL Solvent = 130.0mL ≈ 130. or 1.3×102 mL solute 200.0 ×100 = 35.0% − Solute = 70.0mL

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**Parts Per Million (ppm)**

Solute Solution ×106 1 ppm = 1mg/L

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Example 5 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

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Example 6 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

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**So change the mL into L and the g into mg**

Example 7 150 mL of an aqueous sodium chloride solution contains g NaCl. Calculate the concentration of NaCl in parts per million (ppm). Remember 1ppm = 1 mg/L So change the mL into L and the g into mg 0.0045g 1000mg 1000mL 150mL g L = 30 mg/L = 30 ppm

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**Example 8 Convert 0.0035% NaCl by mass into parts per million of NaCl.**

* Think of % like your grade on a test; % means out of 100 0.0035 100 ×106 = 35ppm

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