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SOLUTIONS

SOLUTIONS. HONORS CHEM 2018. TERMS. Solution : a homogeneous mixture containing particles the size of a typical ion or covalent molecule. (0.1–2.0 nm in diameter) Colloid : a homogeneous mixture containing particles with diameters in the range 2–500 nm (ex- milk)

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SOLUTIONS

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  1. SOLUTIONS HONORS CHEM 2018

  2. TERMS • Solution: a homogeneous mixture containing particles the size of a typical ion or covalent molecule. (0.1–2.0 nm in diameter) • Colloid: a homogeneous mixture containing particles with diameters in the range 2–500 nm (ex- milk) • Suspensions are mixtures with even larger particles, but they are not considered true solutions because they separate upon standing. (ex- orange juice; some liquid medicines that you must ‘shake well’) • Solute: the dissolved substance in a solution • Solvent: the major component in a solution SOLUTION AND SOLUBILITIES

  3. A solution is saturated when no additional solute can be dissolved at a particular temperature • A Supersaturatedsolution can form when more than the equilibrium amount of solute is dissolved at an elevated temperature, and then the supersaturated solution is slowly cooled. • An Unsaturated solution is formed when more of the solute could dissolve in it at a particular temperature. SOLUTION AND SOLUBILITIES

  4. KINDS OF SOLUTIONS SOLUTION AND SOLUBILITIES

  5. SOLUTION AND SOLUBILITIES

  6. SOLUBILITY • The amount of solute per unit solvent required to form a saturated solution is called the solute's Solubility. • When two liquids are completely soluble in each other they are said to be Miscible. • Solubility is effected by Temperature. With increase in temperature solubility of most of the substances increases. • Most gases become less soluble in water as the temperature increases. SOLUTION AND SOLUBILITIES

  7. SOLUBILITY CURVE GRAPH OF SALTS IN WATER SOLUTION AND SOLUBILITIES

  8. What is Molarity and why is it important? • M = moles/L of SOLUTION (not solvent!) • Labs may ask you to prepare a solution of a given concentration • You will be able to use the concentration (molarity) to determine how many GRAMS of a substance should be used to make that solution

  9. Vocabulary • Molarity (M) = 1 mol / 1 L of solution • The higher the Molarity, the higher the Concentration • Why do we care? • Used to make chemical solutions

  10. Molarity Example Problem #1 • How many grams of NaCl are required to make 0.500L of 0.25MNaCl? • 0.500 L sol’n SOLUTION AND SOLUBILITIES

  11. # of moles Concentration = volume (L) V = 250 mL n = 8 moles [ ] = 32 molar V = 1000 mL V = 1000 mL V = 5000 mL n = 2 moles n = 4 moles n = 20 moles Concentration = 2 molar [ ] = 4 molar [ ] = 4 molar

  12. How it’s done • List GIVEN and WANT • Determine the molar mass • Use units and unit factor method (Dim. Analysis) to cancel and solve

  13. Molarity Example Problem #1 • How many grams of NaCl are required to make 0.500L of 0.25M NaCl? 0.500 L sol’n 0.25 mol NaCl 1 L sol’n 58.44 g NaCl 1 mol NaCl = 7.3 g NaCl

  14. Molarity Example Problem #2 • Find the molarity of a 250 mL solution containing 10.0 g of NaF. 10.0 g NaF 1 molNaF 41.99 g NaF 0.25 L sol’n = 0.95MNaF

  15. Solutions dilutions

  16. How do you dilute a solution? • Dilute – make a solution weaker by adding water or another solvent M1V1 = M2V2 • M = Molarity • V = Volume • 1 = initial • 2 = final

  17. Dilution • Preparation of a desired solution by adding water to a concentrate. • Moles of solute remain the same.

  18. Moles of solute before dilution Moles of solute after dilution = Dilution Add Solvent Concentrated vs. Dilute

  19. Dilution Example Problem • What volume of 15.8M HNO3 is required to make 250 mL of a 6.0M solution? GIVEN: M1 = 15.8M V1 = ? M2 = 6.0M V2 = 250 mL WORK: M1 V1 = M2 V2 (15.8M)V1 = (6.0M)(250mL) V1 = 95 mL of 15.8M HNO3

  20. Dilution Problem #2 • Example #1: 53.4 mL of a 1.50 M solution of NaCl is on hand, but you need some 0.800 M solution. How many mL of 0.800 M can you make?

  21. Solution Solution: Using the dilution equation, we write: (1.50 mol/L) (53.4 mL) = (0.800 mol/L) (x) x = 100. mL Notice that the volumes need not be converted to liters. Any old volume measurement is fine, just so long as the same one is used on each side. (However, as mentioned above, if you are calculating how many moles of solute are present, you need to have the volume in liters.)

  22. Your turn. • Example #2: 100.0 mL of 2.500 M KBr solution is on hand. You need 0.5500 M. What is the final volume of solution which results?

  23. Solution (2.500 mol/L) (100.0 mL) = (0.5500 mol/L) (x) x = 454.5454545 mL (oops, my fingers got stuck typing. Bad attempt at humor, really bad!) x = 454.5 mL

  24. Dilution Practice Pick up WS and complete

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