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Concentrations of Solutions

Concentrations of Solutions

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Concentrations of Solutions

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  1. Concentrations of Solutions • Concentration measures exactly how much solute is in a certain amount of solvent. • Parts per Million (ppm or mg/L) • Parts per Billion (ppb)

  2. Acceptable lead levels in drinking water [http://www.mwra.state.ma.us/mw2002ccrmain/assets/leadgraph.jpg]

  3. Concentrations of Solutions • If chlorine levels are 3.0 ppm in drinking water what does this mean in terms of grams of water? 1 million H2Omolec. 1 mole H2O 6.02 x 1023 molec. 1.66 x 10-18 moles H2O

  4. 1.66 x 10-18 moles H2O 18.0 g H2O 1 mol H2O = 2.988 x 10-17 g H2O Or… 3 chlorine atoms in every 0.000000000000000002988 g of water!

  5. Concentrations of Solutions • For larger concentrations, Molarity (M) can be used:

  6. Concentrations of Solutions • Example: • What is the molarity of a solution where 10.0 g of H2SO4 is mixed in 100.0 mL of water?

  7. 1 mol H2SO4 10.0 g H2SO4 = 0.102 mol 98.1 g H2SO4 0.102 mol = 1.02 mol/L 0.1000 L

  8. Concentrations of Solutions • When only the mass of the solution can be measured, molality (m) can be used:

  9. Concentrations of Solutions • Example: • What is the molality of a solution where 87.8 g of NaCl is mixed with 150.0 g of ice (H2O)?

  10. 1 mol NaCl 87.8 g NaCl = 1.50 mol 58.5 g NaCl 1.50 mol = 10.0 mol/kg 0.150 kg