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29 Cards in this Set
- Front
- Back
Definition of a solution
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homogeneous mixture of two or more pure substances, solute is dispersed uniformly though out the solvent
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intermolecular forces in a solution
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must be strong enough to compete against forces between solute particle and solvent particles
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how does a solution form
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the solvent pulls apart solute particles and surrounds (or solvates) them
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3 processes that affect the energy of a solution
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separation of solute particles
separation of solvent particles new interactions between solute and solvent enthalpy change of the overall process depends on ^H for each of these steps |
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why do endothermic processes occur
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increasing the disorder of a system tends to lower the energy of the system, so even though enthalpy may increase, the overall energy of a system can still decrease if the system becomes more disordered
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dissolution v reaction
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dissolution is a physical change, you can return to the original solute by evaporating the solvent
if it reacts, it didn't dissolve and you can't get it back |
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types of solutions
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saturated:
-solvent holds as much solute as possible -dissolved solute is in dynamic equilibrium with solid solute particles unsaturated: -less than max amt of solute is dissolved in the solvent supersaturated: -solvent holds more solute than is normal -solution is unstable, crystallization can usually be stimulated by adding a seed crystal or scratching the side of the flask |
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factors affecting solubility
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-polar substances dissolve in polar solvents, nonpolar dissolve in nonpolar
-the more similar the intermolecular attractions the more likely one substance is soluble in another -glucose is very soluble in water while cyclohexane is not -vitamin a is soluble in nonpolar compounds, vitamin c is soluble in water |
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gases in a solution
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-the solubility of gases in water increases with increasing mass
-larger molecules have stronger dispersion factors |
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solubility related to pressure for liquids, solids, and gas
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-the solubility of liquids and solids does not change appreciably with pressure
-solubility of gas in a liquid is directly proportional to its pressure |
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Henry's Law
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S(g)=kP(g)
S(g) is the solubility of a gas, k is Henry's Law constant for that gas in the solvent, P(g) is the partial pressure of the gas |
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solubility related to temperature for liquids solids and gas
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solubility of solid solutes in liquid solvents increases with increased temperature
the opposite is true of gas |
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ways of expressing concentration of a solution
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Mass Percentage
parts per million and parts per billion Mole Fraction (X) Molarity (M) mol/L Molality (m) mol/kg (with density you can change between the molarity and molality) |
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Colligative Properties
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*changes in colligative properties depend on number of solute particles, not on the identity
-vapor pressure lowering -boiling point elevation -melting point depression -osmotic pressure |
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vapor pressure
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vapor pressure of a solution is lower than the pure solvent
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Raoult's Law
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partial pressure
P(a)=X(a)P*(a) X(a)=mole fraction P*(a)=normal vapor pressure of pure solvent |
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Boiling Point Elevation and Freezing Point Depression
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solutions have higher boiling point and lower freezing point than pure solvent in non volatile interactions
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The van't Hoff Factor
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reassociation is more likely at higher concentrations, there for the number of particles present is concentration dependent (represented by "i")
i= ^T measured/^Tcalculated |
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osmosis
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substances can form semipermeable membranes, allowing some smaller particles through while blocking other. usually allows water, but not solutes
-net movement from the area of higher solvent concentration to the area of lower solvent concentration |
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osmotic pressure
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pressure required to stop osmosis (pi)
pi=(n/V)RT=MRT |
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what is chemical kinetics
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studies the rate at which a chemical process occurs
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factors that affect reaction rates
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-physical state of the reactants
-concentration of reactants -temperature -presence of a catalyst |
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how to determine reaction rate
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monitor the change in concentration of either reactants or products as a fuction of time
average rate= ^[X]/^t |
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rate law
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an equation that shows how the rate depends on the concentration of the reactants
-exponent tells the order of the reaction |
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how to find overall reaction order
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adding the exponents of the reactants
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rate law for a general reaction
aA + bB = cC + dD |
rate=k [A]^m [B]^n
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determining unit for rate constant (k)
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k= unit of rate/ unit of concentration ^2
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integrated rate law for a first order process
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ln [A]t/[A]0 = -kt
ln [A]t - ln [A]0 =-kt [A]0 is initial concentration [A]t is the concentration at time t |
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first or second order process by graphing a line
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makes a straight line- first order
curved line- 2nd order |