Oceans Flashcards
most ionic substances only dissolve in….
polar solvents
most covalent substances only dissolve in….
non-polar solvents
ionic solids dissolve in…
to make….
water
aqueous solutions
standard lattice enthalpy is….
the enthalpy change when 1 mol of an ionic lattice is formed from its gaseous ions under standard conditions
lattice enthalpy is always….
because….
negative
bonds are being broken and energy is being released
the more negative the lattice enthalpy….
the stronger the bonding
enthalpy change of hydration ions is…
the enthalpy change when 1 mol of aqueous ions is formed from gaseous ions
the enthalpy change of solution is….
the enthalpy change when 1 mol of an ionic substance dissolves enough to form an indefinitely dilute solution
you can use a _______ _____ or _____ _____ _____ to find the enthalpy change of solution
enthalpy cycle
enthalpy level diagram
charge density of an ion =
charge / radius
ions with higher charge density have more exothermic lattice enthalpy, why?
the ions are better at attracting each other so ionic bonds are stronger. meaning more energy is released when bonds are made
ions with higher charge density have more exothermic hydration enthalpy, why?
ions are better at attracting water molecules so the intermolecular bonds are stronger. meaning more energy is released when bonds are made
entropy, S, is…
a measure of the number of ways that particles can be arranged and the number of ways the energy can be shared out between particles
how does physical state affect entropy?
solids - hardly any disorder
liquids - some disorder
gases - most disordered
which physical state has the highest entropy?
gas
which physical state has the lowest entropy?
solid
how does no. of moles affect entropy?
when no. of moles increases, entropy increases
ΔtotS =
ΔsysS + ΔsurrS
ΔsysS =
S products - S reactants
ΔsurrS =
-enthalpy change / T (k)
a feasible reaction is….
one that once started will carry on to completion without zero energy being supplied to it
for a reaction to be feasible the total entropy change must be…
positive or zero
the equation for finding the temperature for a feasible reaction to occur is…
T = ΔH / ΔsysS
Ksp is….
the solubility product
when a sparingly soluble solid is dissolved in water to give a saturated solution…
an equilibrium is established
for the reaction
AaBb (s) –> aA^b+ (aq) + bB^a- (aq)
write the expression for Ksp
(A^b+(aq))^a + (B^a-(aq))^b
for the reaction
AB (s) —> A+ (aq) + B- (aq)
write the equation for Ksp
Ksp = (solubility of AB)^2
a neutral solution is one where…
H+ conc = OH- conc
pH =
-log10 [H+]
strong acids are..
monoprotic
monoprotic means…..
each mole of acid produces one mole of hydrogen ions
[H+] =
10 ^-pH
water can act as…
a base and an acid
Kw is…
and is only used for finding the…
the ionic product of water
pH of strong acids
Kw =
[H+] [OH-]
Ka is..
and is only used for…
acid dissociation constant
weak acids
Ka =
[H+]^2 / [HA]
pKa =
-log10 Ka
a buffer is..
a solution that resists changes in pH when a small amount of acid or base are added or it’s diluted
acidic buffers are made by..
mixing a weak acid with one of its salts
in acidic buffers the weak acid…
and the salt..
slightly dissociates
completely dissociates
if you increase the conc of acid in the buffer
the [H+] conc increases shifting equilibrium to the LHS and pH doesn’t change
if you increases the conc of the base in the buffer
the [OH-] conc increases shifting eqm to the RHS and pH doesnt change
the types of radiation that reaches the Earth’s surface are
visible light and UV
the type of radiation that the Earth emits is
infrared radiation (heat)
the ‘IR’ window is…
the range of IR frequencies that are not absorbed by atmospheric gases so escapes into space
the main greenhouse gases are…
water vapour
methane
CO2
greenhouse gases absorb ________ to make bonds in the molecule _____ more. this extra vibrational energy is _________ on to other molecules in the air by ________ , giving the other molecules more kinetic energy so raising the overall ________
IR radiation
vibrate
passed
collisions
temperature
a bronsted lowry acid is a….
proton donator
a weak acid is…
one that partially dissociates
For the ion H2PO4-
state the conjugate base
HPO4^2-
For the ion H2PO4-
state the conjugate acid
H3PO4^-
what factors determine the pH of a buffer solution?
- Ka
- temperature
what is meant by the term conjugate acid-base pairs?
two species differing in H+
in water strong acids..
dissociate completely
in water strong bases…
ionise completely
a Bronsted Lowry base is a…
proton acceptor
in water weak acids….
only dissociate slightly
what is transferred when acids and bases react?
protons
for strong monoprotic acids [H+] =
[acid]
if given the pH of a solution you can calculate the [H+]
10^-pH
what is the pH of a strong base at 298k given by?
pH = 14 + log[OH-]
