Chem 1040: Test 1

Front 1

Definition of a solution

Back 1

homogeneous mixture of two or more pure substances, solute is dispersed uniformly though out the solvent

Front 2

intermolecular forces in a solution

Back 2

must be strong enough to compete against forces between solute particle and solvent particles

Front 3

how does a solution form

Back 3

the solvent pulls apart solute particles and surrounds (or solvates) them

Front 4

3 processes that affect the energy of a solution

Back 4

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

Front 5

why do endothermic processes occur

Back 5

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

Front 6

dissolution v reaction

Back 6

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

Front 7

types of solutions

Back 7

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

Front 8

factors affecting solubility

Back 8

-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

Front 9

gases in a solution

Back 9

-the solubility of gases in water increases with increasing mass
-larger molecules have stronger dispersion factors

Front 10

solubility related to pressure for liquids, solids, and gas

Back 10

-the solubility of liquids and solids does not change appreciably with pressure
-solubility of gas in a liquid is directly proportional to its pressure

Front 11

Henry's Law

Back 11

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

Front 12

solubility related to temperature for liquids solids and gas

Back 12

solubility of solid solutes in liquid solvents increases with increased temperature
the opposite is true of gas

Front 13

ways of expressing concentration of a solution

Back 13

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)

Front 14

Colligative Properties

Back 14

*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

Front 15

vapor pressure

Back 15

vapor pressure of a solution is lower than the pure solvent

Front 16

Raoult's Law

Back 16

partial pressure
P(a)=X(a)P*(a)
X(a)=mole fraction
P*(a)=normal vapor pressure of pure solvent

Front 17

Boiling Point Elevation and Freezing Point Depression

Back 17

solutions have higher boiling point and lower freezing point than pure solvent in non volatile interactions

Front 18

The van't Hoff Factor

Back 18

reassociation is more likely at higher concentrations, there for the number of particles present is concentration dependent (represented by "i")
i= ^T measured/^Tcalculated

Front 19

osmosis

Back 19

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

Front 20

osmotic pressure

Back 20

pressure required to stop osmosis (pi)
pi=(n/V)RT=MRT

Front 21

what is chemical kinetics

Back 21

studies the rate at which a chemical process occurs

Front 22

factors that affect reaction rates

Back 22

-physical state of the reactants
-concentration of reactants
-temperature
-presence of a catalyst

Front 23

how to determine reaction rate

Back 23

monitor the change in concentration of either reactants or products as a fuction of time
average rate= ^[X]/^t

Front 24

rate law

Back 24

an equation that shows how the rate depends on the concentration of the reactants
-exponent tells the order of the reaction

Front 25

how to find overall reaction order

Back 25

adding the exponents of the reactants

Front 26

rate law for a general reaction
aA + bB = cC + dD

Back 26

rate=k [A]^m [B]^n

Front 27

determining unit for rate constant (k)

Back 27

k= unit of rate/ unit of concentration ^2

Front 28

integrated rate law for a first order process

Back 28

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

Front 29

first or second order process by graphing a line

Back 29

makes a straight line- first order
curved line- 2nd order