Exam 3 Flashcards
Solution
homogeneous mixture (uniform) of two or more substances
Solute
component of a solution that is present in lesser quality than the solvent
solvent
solution component presented in the largest quality
aqueous solution
when the solvent is water
electrolytes
formed from solutes that are soluble ionic compounds that disassociate in solution to produce ions that behave as charge carriers; they conduct energy
true solution
homogeneous mixture with uniform properties throughout
pure substance
has only one component (ie water)
true substance
has more than one substance; and is homogeneous throughout solution (particles are not large enough to scatter light)
colloidal susbention
has solute particles distributed throughout a solvent; but it is not completely homogeneous **larger particles, not identical, particles participate.
whats the difference between a solution particle and precipitant?
1nm = solution particles
particles larger than 200nm are precipitates
suspension
heterogenous mixture that contains particles much later than colloid suspension (overtime particles settle at bottom and form second phase)
solubility
how much solute can dissolve in a given volume of solvent
what affects the solubility?
- polarity of solute & solvent-like goes with like (more similar the more they dissolve & greater distance, the less soluble the solute)
- temperature- increased temp increased solubility (usually)
- pressure (little affect on solids & liquids)
saturated solute
when a solution contains all the solute that can be dissolved at a particular temperature **increased temp, you can dissolve more- decreased temp it will dissolve less
supersaturated solute
as solute is cooling, the excess solute may remain in a solution only for a portion of time before the excess will fall to the bottom… It is unstable
What is a dynamic equilibrium?
When an excess solute is added to solvent, it begins to dissolve & contains until it establishes a “dynamic equilibrium btwn dissolved and undissolved.
What is Henry’s Law?
equation?
the number of moles of a gas dissolve in a liquid at a given temp to proportionally to the pressure of gas…
-solubility is directly proportional to pressure of gas in atmosphere… temp must stay the same
Equation:
M=kp (at fixed temp)
**solubility increases at lower temp, decreases at higher temp.
concentration:
the amount of solute dissolved in a given amount of solution. Has a profound effect on properties of solution.
- Physical- melting point & boiling point
- Chemical- solution reactivity
How do you calculate the mass to volume percent of a concentration?
concentration= m (amount of solute in g)/ v (amount of solution in mL) X 100 —which will give the percent of concentration
How do you calculate the mass to mass percent of a concentration?
percent of mass/mass = (g solute)/(g of solution) X 100
How do you calculate the parts per thoustand (ppt) and parts per million of a concentration %?
PPT= g solute/g solution X 10 to the third
PPM= g solute/ g solution X 10 to the sixth
Molarity
M = moles of solute/L solution
What is the equation for a dilution?
M1V1=M2V2
what are the 4 colligative properties?
1: Vapor Pressure Lowering
2: Freezing point Depression
3: Boiling point elevation
4: osmotic pressure
calculating molality?
molality= mol solute/kg solvent
diffusion
net movement of solute or solvent molecules from an area of high concentration to an area of low concentration
concentration gradient
the area where the concentration decreases over distance
selective permeable membrane
a membrane that only allows small molecules to pass through freely, larger molecules & highly charged ions are restricted to cross
semipermeable membranes
a membrane that allows a solvent but not the solute to diffuse from one side to the otehr
osmosis
is the diffusion of a solvent (water) through a semipermeable membrane in response to a water concentration gradient.
osmotic pressure
the pressure that must be exerted to stop the flow of water across a semipermeable membrane by osmosis
osmolarity
the molaritry of particles in solution
hypotonic solution
a solution that has a lower osmolarity
hypertonic solution
a solution with a greater osmolarity
what is the calculation for an equivalent?
eq/l = (eq/mol ion) (mol ion/L) then goes to.... M= (mol ion/L) then to... eq/L = (eq/ mol ion)M
what are the three basic laws about thermodynamics?
1: Energy cannot be created nor destroyed (only converted from one form to another)
2: the universe spontaneously tends towards increasing disorder or randomness
3: The disorder of a pure, perfect crystal @ absolute zero (O Kelvin) is zero
heat flow
transfer of the thermal energy to the surroundings
system
only contains the process that is under study
surroundings
encomposed as the rest of the universe (energy can either be lost from the system to the surroundings or energy can be gained by the system from the surroundings.)
The first law of thermodynamics?
energy of the universe is constant (cannot be created nor destroyed)
exothermic
energy leaves the system during chemical reactions (gives off heat)
endothermic
energy enters system during chemical reactions (takes in heat, to break bonds)
enthalpy
term used to represent heat (delta H)
- delta H + = if energy is absorbed in a reaction (endothermic)
- delta H - =energy is released in reaction, exothermic
entrophy
measure of the randomness of a chemical system (delta S)
- delta S + = exothermic & spontaneous
- delta S - = endothermic & nonspontaneous
which one has greater entrophy?
He (s) or Na (s)
H2O(l) or H2(g)
Na
H2O liquid
what is the 2nd law of thermodynamics?
everything in the universe is spontaneous & tends toward increasing disorder or randomness (entropy)
free energy
equation?
delta G; represents the combined contribution of the enthalpy and entropy values for a chemical
formula: delta G = (delta H) - (T) X (delta s)
- delta G + = always spontaneous
- delta G - = never spontanous
calorimetry
the measurement of heat energy changes in a reaction
calorimeter
device that measure heat changes in calories
specific heat
equation?
SH of a substance is defined as the number of Calories of heat needed to raise the temp of 1g of substance 1 deg of C.
We need to know SH; mass of solute, temperature change
Q= (m) X (delta T-change in temp) x (SH)
what is the SH of water?
I Cal/g degree of C
activation energy
the minimum amount of energy required to initiate a chemical reaction
activated complex
an extremely unstable, short lived intermediate complex
what factors affect reaction rates?
1: structure of reacting species (opposite charges react faster, same charges have no reaction & if it is already dissociated than it has a low activation energy)
2: molecular shape & orientation
3: concentration of reactant (increased concentration, increased rate)
4: temperature of reactants (temp increase = rate increase)
5: physical state of reactants (how far apart the particles are/how often them collide ( liquids>gas>solid)
6: presents of a catalyst (increases reaction rate)
higher kinetic energy rate order:
liquids>gas>solid
equilibrium reactions
chemical reactions that do not go to completion; represented by reactants only:
rate= k(r) –depending on if it is first order or second order the (r) will be to that power
**once it reaches an equilibrium then it will be balanced.
reversible reaction
equation?
a process that can occur both ways
keq = products/reactions
**comes from a balanced equation; the product or reactant can be to a specific power depending on how many ions of that particular
dynamic equilibrium
when the rate of the forward process in a reversible rate is exactly balanced by the rate of the reverse process.
ie: N2 + 3H2 = 2NH3
rate r= kr [N2] [H2] to the third power
rate f= kf [NH3) to the second power
(product over reactant)
what happens when you have a
larger k constant?
smaller k constant?
larger - more products
smaller- more things stay in reactant form
what is LeChaletier’s principle?
if a stress is placed on a system that is at equilibrium, the system will despond by altering the equilibrium composed in such a way to minimize stress.
ie:
product introduced - shift to the right
reactant introduced - shift to the left
