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AP Chemistry – Solutions

AP Chemistry – Solutions. solution : homogeneous mixture; solid, liquid, or gas. solvent : substance present in the greatest amount. solute : also present;. there might be more than one. +. –. –. –. –. –. –. +. +. +. +. +. +. H. H. H. H. H. H. H. H. H. H. H. H. –. –.

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AP Chemistry – Solutions

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  1. AP Chemistry – Solutions

  2. solution: homogeneous mixture; solid, liquid, or gas solvent: substance present in the greatest amount solute: also present; there might be more than one

  3. + – – – – – – + + + + + + H H H H H H H H H H H H – – – – – – + + + + + + O O O O O O Intermolecular forces (IMFs) operate between solvent and solute particles. Solutions form when solute-solvent IMFs are comparable to solute-solute IMFs. Solvation/hydration = “glomming” d+ d+ solvent particles “pull” solute ions from the crystal -- d– solvent particles surround solute particles (if solvent is H2O, we say “hydration”) -- then solvation:

  4. (3) above isn’t very (–) for oil and water and, with (1) and (2) requiring energy input, this doesn’t form a solution. Energy Changes and Solution Formation (1) solute particles are separated from the crystal lattice; DH1 > 0 (2) solvent particles separate to make room for solute particles; DH2 > 0 (3) solvent and solute particles are attracted to each other; DH3 < 0 S = DHsoln -- If DHsoln is too (+) (i.e., too endo), soln won’t form.

  5. The enthalpy of solution formation (i.e., DHsoln) for ammonium nitrate is (+), but the system’s disorder increases from NH4NO3(s) to NH4+(aq) + NO3–(aq), and so solution formation is still spontaneous. For polar/nonpolar, (3) isn’t (–) enough, and (1) and (2) lead to a DHsoln that is too (+). Spontaneous processes tend to occur... exo (A) when DHsoln is (–), (i.e., ____) (B) when the disorder of the system increases ** NOTE: (B) is MORE influential in determining whether or not soln forms

  6. Sometimes it is not readily apparent whether a solution has been formed or whether a chemical reaction took place. To help you decide, consider the following: If the product is evaporated to dryness, a solution would give you what you started with. e.g., NaCl(s) + H2O(l)  NaCl(aq) (SOLN) (RXN) Ni(s) + 2 HCl(aq)  NiCl2(aq) + H2(g)

  7. solution crystallization A saturated solution of NaCl, in which the rates of solution and crystallization are equal. Solubility Crystallization is the opposite of the solution process. SOLUTE + SOLVENT SOLUTION -- When the rates of solution and crystallization are equal, __________ is established. equilibrium

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