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Solutions

Solutions. Solutions. Solutions are homogeneous mixtures, you can not distinguish the components with the eye. Air can be considered a solution: – 80 % of air is nitrogen gas, making nitrogen the solvent or majority component.

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Solutions

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  1. Solutions

  2. Solutions • Solutions are homogeneous mixtures, you can not distinguish the components with the eye. • Air can be considered a solution: • – 80 % of air is nitrogen gas, making nitrogen the solvent or majority component. • – 19 % of air is oxygen gas, making oxygen the solute or minority component. Finding Solutions

  3. Solutions • One characteristic of a solution is a variable composition. For example, the quality of air is affected by the quantity of various pollutants. • – The proportion of a solute is important information and is called the concentration of a solution. Finding Solutions

  4. Mass Percent • The simplest recipe for a solution tells us how many grams of a solute there is in 100 grams of solution. This way of expressing concentration is called mass percent: • mass percent = mass of solute x 100 % • mass of solution Concentration

  5. Mass Percent • Example 1: • Solution A contains 10 g of salt in 90 g of water. • Solution B contains 20 g of salt in 80 g of water. • a) Which solution is more concentrated? • Solution A  10 g/ 90 g = 0.11 • Solution B  20 g/ 80 g = 0.25 • b) What is the mass percent of each solution? • Solution A  (10 g/ 100 g) x 100 % = 10 % • Solution B  (20 g/ 100 g) x 100 % = 20 % Concentration

  6. Mass Percent • Example 2: • In a 0.90 % sodium chloride solution, there are 0.9 g of sodium chloride and 99.1 g of water for every 100 g of solution. • a) What mass of salt would you need to prepare 500 g of solution? • mass percent = mass of solute x 100 % • mass of solution Concentration 99.1 g H2O 0.90 g NaCl

  7. Mass Percent • Example 2: • a) 0.90 % = mass of solute x 100 % • 500 g • (0.90 %)(500 g) = mass of solute • 100 % • 4.5 g = mass of solute (NaCl) Concentration

  8. Mass Percent • Example 2: • b) What mass of water would you need? • mass of water = 500 g (solution) – 4.5 g (solute) • = 495.5 g Concentration

  9. g / L • Concentration may also be expressed in grams of solute per liter of solution. • Example 2: What mass of sugar do you need to make 300 ml of a 5.00 g/L sugar solution? • Step 1 • Concentration (g/L) = mass of solute (g) • volume of solution (L) • 5.00 g/L = mass of solute (g) • 0.3 L Concentration

  10. g / L Example 2: Step 1 (cont’d) (0.3 L)(5.00 g/L) = mass of solute (g) 1.50 g = mass of solute (sugar) Step 2 (How to mix together) Place 1.50 g sugar in beaker and add enough water to make 300 ml of sugar solution. Concentration

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