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Changes in Solubility. Pressure A. Changes in pressure do not affect solubility of liquid or solid solutes in liquid solvents. 1. But, increases in pressure do increase the solubility of a gas in liquids. II. Temperature
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Changes in Solubility • Pressure A. Changes in pressure do not affect solubility of liquid or solid solutes in liquid solvents. 1. But, increases in pressure do increase the solubility of a gas in liquids. II. Temperature A. Increasing the temperature usually increases the solubility of solids in liquids. B. But, increasing temperature decreases the solubility of gases in liquids. ** This is important for fish in the winter, since colder temperature means more O2 in water which is good since fish move less in cold water. **
Molarity • I. Concentration of Solutions • A. Concentration-DEF- a measure of the amount of solute in a given amount of solvent or solution. • 1. There are two ways in order to express concentration. • a. Molarity • b. Molality • B. Molarity-DEF- the number of moles of solute in one liter of solution.
1. In order to find the molarity of a solution, you must know the molar mass of the solute. • Ex- a one molar concentration of NaOH would be written- 1M NaOH • 2. Formula • Molarity (M) = amount of solute (mol) • volume of solution (L) • 3. The molarity of any solution can be calculated by dividing the number of moles of solute by the number of liters of solution.
Example #1 • Ex. You have 3.5L of a solution that contains 90.0 g of sodium chloride, NaCl. What is its molarity? • Given: 90.0 g NaCl, 3.5 L • ? – molarity • You NEED moles & Liters…..so you must convert grams to moles. 1 mol NaCl = 58.5 g NaCl (molar mass) * 90.0 g 1 mol NaCl 58.5 g NaCl = 1.54 mol NaCl M = mol/L so… plug in your numbers AND…. M= 1.54 mol NaCl/ 3.5 L of solution (from problem) = 0.44M NaCl (for each 1 liter of solution)
Example #2 • Ex. You have 0.8 L of a 0.5 M HCl solution. How many moles of HCl does this solution contain? • Given: 0.8 L and 0.5 M HCl • ? – moles of HCl • * You need to rearrange the formula for molarity so…. • Moles = volume x molarity • SO…. • moles= 0.8 L x 0.5 M HCl = 0.4 moles of HCl