Solutions and Solubility Flashcards
solution
a homogenous mixture
homogenous mixture
has uniform composition
What are MCAT solutions generally?
solids dissolved in liquids
Saturation and units
how much solute is dissolved
g/L
When will a precipitate form?
adding more solute to an already saturated solution
or decreasing the solubility of a solution
When is a solution saturated?
a solution is saturated when concentrations of reactants are equal to Ksp
Ways to decrease the solubility of a solution?
through the common ion effect or by changing temperature/pressure
Do most dissolutions change temperature or pressure?
yes. most solutions are endothermic and require heat, which lowers the environment’s temp.
Most dissolutions also increase pressure.
supersaturated
more than max solute is dissolved in solution
electrolyte
ions in solution that can conduct electricity
What does a higher temperature do to solubility of an ionic compound?
increases solubility
most dissolutions are endothermic and require heat
What does a lower temperature do to solubility of an ionic compound?
decreases solubility
most dissolutions are endothermic and require heat
Relationship between solubility of a gas and temperature
Lower temperature makes the gas less soluble
Gas has less energy to escape the solution
Alkali metals solubility
always soluble in H2O
What molecules are always soluble?
nitrates, chlorates, and acetates
Halides solubility
always soluble unless with Ag, Pb or Hg
Halide atoms
F, Cl, Br, I
SO4 2- solubility
always soluble expect with Ca, Sr or Ba
What molecules are generally insoluble?
carbonates, phosphates, S2- and sulfates
except with alkali metals that are always soluble
Are oxides generally soluble or insoluble?
generally insoluble
except for with Ca, Sr, Ba or alkali metals
Molarity
M
moles of solute / liter of solution
Molality
m
moles of solute / kg of solvent
For water, one liter equals
one kilogram
For water, one mL equals
one gram
When do we use molality?
when discussing colligative properties
colligative properties
properties changing solely with concentration of a solution
ex: adding salt to H2O lowers freezing point
Normality
number of equivalents / liter of solution
When do we use normality?
in acid-base chemistry
the equivalents are H+ or OH- ions
How can we get molarity from normality of an acid?
N = M(acid) * H+ in acid molecule
How can we get molarity from normality of a base?
N = M(base) * OH- in base molecule
What does Ksp tell us?
how soluble something is
Relationship between Ksp and solubility
higher Ksp = more soluble
What is Ksp formula generally?
= [anions] [cations]
*solid reactant and pure water are not included in formula
When Q>Ksp what happens?
a precipitant forms
maybe not right away, solution could be supersaturated for a little
When saturated what rates are equal?
rates of dissolution and precipitation, ie. forward and reverse reactions
common ion effect
solubility of an ionic species decreases when one of its component ions is already present in solution
How does common ion effect theoretically work?
since some reactant is already present, less solute can dissolve before Ksp is reached
means that we have less solubility
shifts reaction towards the solid reactant
Where do we see the common ion effect?
in acid base chemistry
ex: having a basic solution (more OH-), might make Pb(OH)2 less soluble
Can you shift a dissolution towards the reactants?
sure
can use a coordination complex around a metal to remove ions from the solution
Weak electrolyte
does not produce many ions when dissolved in solution
