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Solutions

Solutions . Calculation of concentrations Solubility of solutes. solvent. solute. solution. Definition of molarity. Ammonia, NH 3 , has a molar mass of 17.0 g/mol. (a) If 17.0 g of NH 3 is dissolved in enough water to make 1.00 L of solution, what is the molarity of the solution?

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Solutions

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  1. Solutions • Calculation of concentrations • Solubility of solutes

  2. solvent solute solution

  3. Definition of molarity • Ammonia, NH3, has a molar mass of 17.0 g/mol. • (a) If 17.0 g of NH3 is dissolved in enough water to make 1.00 L of solution, what is the molarity of the solution? • (b) If 17.0 g of NH3 is dissolved in enough water to make 2.00 L of solution, what is the molarity?

  4. (b) If 17.0 g of NH3 is dissolved in enough water to make 2.00 L of solution, what is the molarity? • (a) • (b)

  5. Definition of molality • Ammonia, NH3, has a molar mass of 17.0 g/mol. If 17.0 g of NH3 is added to 1.00 kg of water, the molality of the solution is:

  6. Note the difference between molaRRRity and molaLLLity

  7. Definition of mass percentage • 10.0 g NH3 are dissolved in 90.0 g water. What is the mass percentage of NH3 in the solution? • Percent is always the part out of the whole:

  8. Definition of mole fraction • Ammonia, NH3, has a molar mass of 17.0 g/mol. Water, H2O, has a molar mass of 18.0 g/mol. If 17.0 g of NH3 and 18.0 g H2O are mixed, the mole fraction of ammonia is

  9. When 2.09 g of NaCl is dissolved in 455 g H2O, what is the molaLLLity of NaCl?

  10. Many (not all) solids become more soluble at higher temperatures

  11. “Like dissolves like” • Polar compounds dissolve well in polar solvents • Non-polar compounds dissolve well in non-polar solvents

  12. Polar solvent molecules are attracted to the polar solute molecules Many polar groups. Water is attracted through dipole-dipole interactions and hydrogen-bonding.

  13. Non-polar molecules tend to dissolve in non-polar solvents Vitamin A is a large, mostly non-polar molecule. It is insoluble in water, but will dissolve in non-polar solvents such as benzene:

  14. Salt dissolving in water

  15. Pressure effects on gas solubility • Increasing the pressure of a gas over a liquid increases the solubility of the gas in the liquid • Henry’s Law: C = kP • C = solubility of gas • P = pressure of gas (above liquid) • k = (Henry’s Law) constant • k depends on both the gas and the solvent

  16. Higher pressure increases rate of gas molecules dissolving into solution

  17. Reminder: • Learn definitions of concentration units: • M = moles solute / L of solution • m = moles solute / kg of solvent • χA = moles A / total moles

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