Lecture 4

what is a solution
it is a homogenous mixture of two or more compounds in a single phase: liquid, solid and or gas
give an example of a solid solution
brass: zinc and copper
what is an ideal solution
solutions made from compounds that have similar properties-for instances: a solution of benzene and toluene-similar size and similar bonding properties
what is an ideally dilute solution
the solute is completely seperated by the solvent, so  there are no interactions between them

give examples of a colloidal system

 

and 

 

a brief description of it

aerosal, foam, an emulsion (milk or butter) & sol (paint)

 

so, this is a solution only the solute particles are usually too small to be extracted by filtration

what is coagulation
heating or introducing a solute into a colloidal system-the larger particles will settle out and then can be filtered out
how are ionic compounds dissolved
solvation- ionic bonds are dissolved into a polar solvent, so that the cations and anions form bonds with their oppositely charged ends of the polar solvent
what does the compound nitrite look like
NO2-
what does the compound hypochlorite look like
ClO-
what is molarity
moles of the compound divided by the volume of the solution
what is molality
moles of solute divided by kilograms of solvent
what is mole fraction
the number of moles of solute divided by the total number of moles in solution
what is mass percentage
mass of the solute divided by the total mass of the solution times 100
what is parts per million
mass of solute divided by total mass of solution times 10^6

context: acid-base reaction

 

what does is mean if H2SO4 is called a 2 normal solution

it means that it can donate 2 protons for each H2SO4
if given the specific gravity (1.006 kg) of a compound, how would you determine how many moles it had within it
since water weighs 1 kg, subtract that form 1.006 kg and you get about 6 g.  6g/ the molecular weight of the compound to get moles
when determining solubility, what should you look for

look for very polar functional groups (N,O) something super electronegative

 

second, look for ionic bonding molecules

 

third, look for non polar (least soluble in water)

context: the air we breathe is approximately 21% O and 79%  . if the partial pressure of nitrogen in air is 600 torr, what can you automatically exclude from this question
partial pressure refers to number of particles not, the mass
at constant pressure, how can you determine the ethalpy of a reaction
well, since at constant pressure the ethalpy of a reaction is equal to the change in heat-ethalpy can be equal to the  change of heat in step 1: breaking of intermolecular bonds in the solute, change of heat in step 2: breaking of intermolecule bonds in the solvent, and change of heat in step 3: formation of intermolecular bonds between solvent and solute

context: solution formation

 

the first two steps are:

 

the last step is:

endothermic and the last step is exothermic
a negative heat of solution results in 
stronger intermolecular bonds and will give off heat
a positive heat of solution results in
weaker intermolecular bonds
since separate pure substances are more orderly than a solution, the overall entropy of the solution what
increases
what is vapor pressure

in an air tight seal, water molecules will break their intermolecular bonds to form water vapors molecules

 

once the molecules leaving the liquid equals the rate of molecules entering the liquid

how can you increase vapor pressure
increase temperature
when does boiling occur
when the vapor pressure of a solid equals the atmospheric pressure
what does Raoult’s law for non volatile solutes say
if 97% of the solution is solvent, then the vapor pressure will be 97% of the vapor pressure of a pure solvent
what does Raoult’s law for volatile solvents say:
if 97% of the solution is solvent, then the vapor pressure will be 97% of the vapor pressure of the pure solvent and 3% vapor pressure of pure solute
given a negative heat of solution, what can be said about that mechanisms vapor pressure
negative heat of solution means stronger intermolecular bonds are formed and vapor pressure is lowered
the solubility product will only change with a change in
temperature
according to le chatalier’s principle, when a common ion effect is added to an already existing ion solution in equilibrium, what will happen
since there is an added ion, it will push it back to the left and form more precipitate
pressure on liquids and solids has little effect, but pressure on a gas;
increases its solubility
when the volatile solute concentration is low, each molecule is surrounded by solvent molecules creating deviation from the behavior of

pure volatile solute

;

thus its vapor partial pressure is not proportional to its pressure as a pure volatile solute

the solubility of salts tends to what with an increase in temeprature
tends to increase too
the solubility of gases tends to what when temperature is increased
gases tend to decrease
when a solution is saturated, what does this mean in terms of solute and solvent concentrations
solute is maximized and solvent is minimized
x

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