CHEM 191 Lecture 3and4 Flashcards
why don’t pure solids and pure liquids appear on reaction quotients or equilibrium constant
because you can’t change the concentration of a pure solid or a pure liquid
what is the formula for reaction quotient and equilibrium constant
products raised to their stoichiometric powers over reactants raised to theirs, pure solids and pure liquids don’t appear
when do we use Kc - equilibrium constant
once the reaction has reached equilibrium
if Q is greater than Kc which way is the reaction going
to the left - products are being turned into reactants
if Q is less than Kc which way is the reaction going
to the right - reactants are being turned into products
at what value ok Kc are there equals amounts of products and reactants
1
what does it mean if Kc is large
the reaction goes further towards completion
what does it mean if Kc is small
the reaction doesn’t go as far towards completion
what is the only thing K depends on
temperature
how can you change pressure
by adding an inert gas or changing the volume
what will the system do if pressure is increased
the system will move to create more gas molecules
will changing pressure by changing volume have an effect on an equilibrium with equal amounts of gas moles on either side of the equilibrium
no, because the volume terms cancel out in the expression for Q
will changing pressure by adding an inert gas have an effect on equilibrium position
no, because there is no term for the inert gas in the expression for Q
what is solubility a measure of
how much solute will dissolve in a given amount of solvent
what is a saturated solution
a solution (at equilibrium) that is formed when the maximum amount of solute is dissolved in a particular volume of solvent at temperature (T)
what does solubility depend on
the chemical nature of the solute and solvent, temperature (T) and pressure for gaseous solutes
when is the equilibrium constant for the dissolution of a slightly soluble salt in water
Ksp - the solubility product
if Qsp is less than Ksp will a precipitate form
no
if Qsp is greater than Ksp will a precipitate form, why?
yes - there are more products (because the formula for Qsp and Ksp is just the concentrations of the products) than the equilibrium can support so in order to reach equilibrium some of those ions precipitate out into a solid
what does the presence of a common ion mean in terms of solubility of an ionic solid
solubility will always decrease in the presence of a common ion
