Properties of Solutions_part_1_S13

Properties of Solutions_part_1_S13 - PROPERTIES OF...

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PROPERTIES OF SOLUTIONS SOLUTION COMPOSITION A solution is a homogeneous mixture of a solvent and solute(s). The solvent is the dissolving substance and the solute is the dissolved substance. Examples: clean air, salt and water, 14K gold. Can you identify the solvent and the solute(s) in each? Solution composition can be described in different terms: Molarity Mass Percent Mole Fraction Molality THE TERMODYNAMICS OF SOLUTION FORMATION We can look at solubility as consisting of three hypothetical steps as shown below: Three steps to form a liquid solution Zumdahl, S. S. Chemical Principles , 6 th ed.; Boston: Houghton Mifflin Company, 2010. 1
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Step 1: Breaking up the solute-solute interactions or expanding it Step 2: Breaking up the solvent-solvent interactions or expanding it Step 3: Forming interactions between solute and solvent particles to form the solution Ehthalpy of the solution (a) Steps in an exothermic reaction, (b) Steps in an endothermic reaction Zumdahl, S. S. Chemical Principles , 6 th ed.; Boston: Houghton Mifflin Company, 2010 We expect the first step to be ----------------------- . This is because -------------------- -----------------------------------------------------. This energy is represented as H 1 . We expect the second step to be ------------------------. This is because ------------------ -----------------------------------------------------. This energy is represented as H 2 . We expect the third step to be -------------------------. This is because -------------------- -------------------------------------------------------. This energy is represented as H 3 . The enthalpy of the solution is therefore, H soln = H 1 + H 2 + H 3 The standard enthalpy of solution is H ° soln = H ° 1 + H ° 2 + H ° 3 The enthalpy of hydration, H ° hyd , is defined as the sum of H ° 2 and H ° 3 2
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Therefore, the standard enthalpy of the solution is: H ° soln = H ° 1 + H ° hyd Example: NaCl in water NaCl(s) Na + (g) + Cl - (g) H ° 1 = 786 kJ/mol H 2
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  • Spring '13
  • fakhreddine
  • Solubility, Solvent, Houghton Mifflin company, dissolution process

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