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Colligative properties

Colligative properties. Solutions Part 4. Electrolytes: a quick review. Electrolytes form ions in solution. Ions allow water to conduct electric current Three types of electrolytes: strong , weak, and non-electrolytes. Strong Electrolytes. Strong electrolytes ionize completely in water.

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Colligative properties

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  1. Colligative properties Solutions Part 4

  2. Electrolytes: a quick review • Electrolytes form ions in solution. • Ions allow water to conduct electric current • Three types of electrolytes: strong , weak, and non-electrolytes.

  3. Strong Electrolytes • Strong electrolytes ionize completely in water. • More ions in the water, more conductivity. • Strong electrolytes include: • Strong acids HCl H+ + Cl- • Strong bases NaOH Na+ + OH- • Soluble salts CaCl2 Ca2+ + 2Cl-

  4. Molarity:review • Moles per liter • 1.0 M = 1 mole solute per 1 liter solution. • Question • What is the molarity of 1.56 g of gaseous HCl in a 26.8 mL solution?

  5. Mole Fraction • mole fraction: the number of moles of a component of a solution divided by the total number of moles of all components.

  6. Example: • 58.5 grams of NaCl are in a one liter solution. • What is the Molarity of the NaCl? • 1 M • 58.5 grams of NaCl are in 1800 grams of water. • What is the mole fraction of NaCl? • 1/101

  7. Molality • Definition: a unit of concentration, defined to be equal to the number of moles of solute divided by the number of kilograms of solvent . This is not to be confused with Molarity

  8. Why so you add salt to an icy sidewalk? • It melts the ice. • How? • Colligative properties. • Why so some types of salt seem to work better than melting the ice than others. • Why? • Colligative properties.

  9. Colligative properties • are properties of solutions that depend on the number of molecules in a given volume of solvent and not on the properties (e.g. size or mass) of the molecules.[1] Colligative properties include: lowering of vapor pressure; elevation of boiling point; depression of freezing point and osmotic pressure.

  10. Colligative properties • How many ions are formed from the dissociation of 1mole of NaCl? • From CaCl2? • From NH4Cl • From H3PO4?

  11. Question • What is the concentration of each type of ion in the following solutions? • 0.50M Co(NO3)2 • 1 M Fe(ClO4)3

  12. Answer • Co 2+ 0.5 M • NO3- 1.0 M • Fe 3+ 1 M • ClO4- 3M • Why isn’t it 3M Cl- and 12 M O2- ??

  13. Vapor Pressure Reduction • The particle act to attract the water molecules making it more difficult for them to free themselves to become vapor.

  14. Freezing point depression • The individual particles interfere with the water’s ability to form a crystal depressing the freezing point.

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