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Special Topics

Special Topics. Math and chemistry review, solutions, and concentrations. http://www.youtube.com/watch?v=lMW5YYiEfgU. Outline. I. Metric system review II. Concentration of solutions A. Solute B. Solvent C. Grams % D. Molarity (M) E. Molality (m)

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Special Topics

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  1. Special Topics Math and chemistry review, solutions, and concentrations http://www.youtube.com/watch?v=lMW5YYiEfgU

  2. Outline I. Metric system review II. Concentration of solutions A. Solute B. Solvent C. Grams % D. Molarity (M) E. Molality (m) F. Osmolality and dissolution G. Sample problems

  3. http://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.htmlhttp://micro.magnet.fsu.edu/primer/java/scienceopticsu/powersof10/index.html

  4. King Henry Slider

  5. Distance, volume, mass and temperature

  6. Scientific Notation • The notation is based on powers of base number 10. The general format looks something like this: • N X 10x • where N= number greater than 1 but less than 10 and x=exponent. • Placing numbers in exponential notation has several advantages. • Concise! • Easier math without your calculator! • Let’s practice!

  7. Now let’s talk about solutions Water is the most abundant liquid on the earth and is necessary for all life. Because of water's great dissolving properties, any sample is a solution containing solids, other liquids, and gases from the environment.

  8. Aqueous solutions • A solution is a homogeneous mixture of ions or molecules of two or more substances. • Two parts • Solvent is the component that is in the largest quantity (water) • Solute is the component that is dissolved in the solvent.

  9. Concentration • A measure of how much of a substance (solute) is dissolved in another substance (solvent) • To calculate [concentration]: • Common usages of concentration: • Mass (m/v) conc. (grams%= grams per 100 ml, etc.) • Molarity (units are moles/L or M) • Molality (units are moles/kg or m) • osmolality

  10. gm % • Let’s practice: • What is the gm% of 5.0 x101 g of NaCl in 100 ml of water? • What about 0.009 gm in 100ml of water? • Of the three ways we will determine a solution’s concentration, this is the easiest one. • Why?

  11. In the case of dilute aqueous solutions, scientists often use the approximation: • Molarity (mol/L) = Molality (mole/kg solvent) • This is a very close approximation for dilute solutions because: • 1) 1 kg of water  1 L • 2) volume of solvent >> volume of solute therefore: • volume of solution  volume of solvent • mass of solution  mass of solvent We are walking sacks of dilute aqueous solutions.

  12. Molality (moles/kg) • What is a mole? • Avogadro’s number: 6.02 x 10 23 • Number of atoms or molecules necessary to reach atomic or molecular mass in grams • How much does one mole of sodium weigh? • Sodium Chloride? • Need periodic table Above I show some pictures: one is a poor representation of a great Italian theoretician: the other a good representation of a poorly spelled Italian theoretician. I implore my students to notice the differences.

  13. Dissociation factor to determine osmolality (dissolution) • Ionic compounds that are soluble in water dissociate completely and exist in solution entirely as ions. • Soluble ionic compounds are strong electrolytes. • NaCl, KCl, MgCl2, HCl, CaCl2 • Molecular compounds such as sugars, proteins, fats and alcohol are non-electrolytes. They have no tendency to come apart, and they exist in solution entirely as aqueous molecules.

  14. What is the osmolality of a 5.4 % glucose solution? Question • Is the solution hyperosmotic, • hypo-osmotic, or isosmotic?

  15. Steps to complete the task • Write out the grams% • Convert to grams per liter (multiply by 1000ml/ 1 Liter) • Convert the grams to moles (you need MW to do this! Multiply by 1mole/mw gms of substance) • multiply by 1,000mmole/Mole to get mmole • You now have mM/L . Multiply by 1L/1kg to convert to molality (mM/kg) • Multiply by the dissociation factor and you now have osmolality! (glucose and proteins are “1”) • The chorus breaks out into song!

  16. 54 gm x 1 mol = .3 mol X 1000mmol = 180 gm L L 1 mole Osmolality of a 5.4 % Glucose Solution MW glucose = 180 gm/mol 5.4 % = 5.4 gm 100ml 5.4gm X 1000ml = 54 gm 100ml L L Isosmotic—what would the cell do? Dissociation factor is one so: 300 mOsm kg

  17. Question • What is the osmolality of a 3.0% NaCl solution? • Is the solution hyperosmotic, • hypo-osmotic, or isosmotic?

  18. 30 gm x 1 mol = .513 mol = For NaCl, 1 mmol = 2 mOsm 513 mmol x 2 mOsm = 1026 mOsm = 1026mOsm/kg 58.5 gm L L L mmol L Osmolality of a 3% NaCl Solution MW NaCl = 58.5 3 % = 3 gm/100ml 3 gm X 1000ml = 30 gm 100ml L L 513mmol/L Hyperosmotic—what would the cell do? In order to understand this concept, you need to learn about body fluid compartments!

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