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77 Cards in this Set

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Arrhenius acid

Any compound that increases the concentration of H+ in aqueous solution

Arrhenius base

Any compound that increases the concentration of OH- in aqueous solution

Common Arrhenius bases

Group 1 and 2 cations

Acid-base reaction (aka neutralization) (with Arrhenius acids and bases)

Arrhenius acid + Arrhenius base --> water + salt

Limitations of Arrhenius definition

only applies in aqueous solution, but acids and bases can exist and react in the gas phase as well

pH

-log[H+]

pOH

-log[OH-]

[H+]

10^(-pH)

[OH-]

10^(-pOH)

pH + pOH = ?


(for any aqueous solution at T = 25C)

14

The two properties of an acid solution that determine pH

strength and concentration

strong acid/base

one that dissociates completely in water

Bronsted-Lowry acid

a species which is capable of donating a proton

Bronsted-Lowry base

a species that is capable of accepting a proton, which requires a lone pair of electrons to bond to the H+

amphoteric

means "can act as an acid or as a base".


usually used in reference to water.

Strong acids/bases ionize/dissociate _____

completely

Weak acids/bases ionize/dissociate _____

only partially

Conjugate base of a Bronsted-Lowry acid

the species formed after the acid has donated its proton

Conjugate acid of a Bronsted-Lowry base

the species formed after the base has accepted a proton

Common strong acids


(there are 6 of them)

HCl (hydrochloric acid)


HBr (hydrobromic acid)


HI (hydroiodic acid)


H2SO4 (sulfuric acid)


HNO3 (nitric acid)


HClO4 (perchloric acid)

Common strong bases

Group 1 and 2 hydroxides

Common weak bases

neutral nitrogen-containing compounds, e.g.


ammonia NH3


trimethylamine N(CH3)3


pyridine C5H5N

pKw at T = 25C

14

Kw at T = 25C

1 x 10^(-14)

pKw in terms of pH and pOH

pKw = pH + pOH

Kw in terms of [H3O+] and [OH-]

Kw = [H3O+][OH-]

Number of mol of water in a liter

56

ratio of H3O+ (or OH-) ions to water molecules in any given volume of pure water

1 to 560,000,000

For what kinds of acids and bases is water's contribution of hydronium ions non-negligible

weak acids and weak bases

Ka

acid dissociation constant.


equilibrium constant for the equation:


HA + H2O --> A- + H3O+

Ka in terms of [HA],[A-], [H3O+]

Ka = [A-][H3O+]/[HA]

Kw in terms of Ka and Kb


(only true for an acid and its conjugate base, or a base and its conjugate acid)

Kw = Ka * Kb

Kb

the base association constant.


the analog of Ka but for bases.


Equilibrium constant for the equation:


B + H2O <-> HB+ + OH-

pKw in terms of pKa and pKb


(only true for an acid and its conjugate base, or a base and its conjugate acid)

pKw = pKa + pKb



A strong acid's conjugate base is ______ in water

neutral

A weak acid's conjugate base is a ____ base


A weak base's conjugate acid is a ____ acid

1. weak


2. weak

For a strong acid, Ka ____ 1

Ka >> 1

Equation for Kb

Kb = [HB+][OH-]/[B]

When strong base reacts with weak acid, resulting solution is _____

basic

When strong acid reacts with weak base, resulting solution is _____

acidic

Effect of temperature on pKw

As temperature increases, pKw decreases


(i.e. Kw increases)

Why does gypsum appear to be more soluble in salt water than in fresh water?

Background ions, or other ions, will tend to shield e.g. Ca2+ and SO4(2-) ions from each other.


even more so if there are Cl- and Na+ ions, respectively, that can contribute even more to this effect.


Therefore e.g. gypsum will appear to be more soluble in salt water than fresh water.

Correction for activity of free ion a_i

ai = m_i * gamma_i




m_i = mass fraction


gamma_i = activity coefficient

Ionic Strength:


what is the equation and what are the units?

I = 1/2 sum_i (m_i * (z_i)^2)




...where _i refers to the ith ion




ionic strength has concentration units

Hydration

when an ion is surrounded and stabilized by water molecules

spectator ions

ions that don't take part in a reaction (esp. a precipitation reaction)

formula for solubility product constant

Ksp = [component 1] * [component 2] * ... * [component n]




e.g. for salt:


Ksp = [Na+][Cl-]

effect of pressure on solubility of a gas

increase in pressure means increase of solubility for the gas

effect of pressure on solubility of solid or liquid

no effect

true/false: pH affects solubility?

true.


(just be aware that it's all concentrations and equilibria, so think it through)

effect of ionic strength on solubility

increase in ionic strength means decrease in solubility, since there are already a lot of ions in solution




(presumably, this is subject to the assumption that some of the ions are the same as the ones already in solution?)

dissolution vs. solubility

solubility is a thermodynamic concept


dissolution is a kinetic concept

pH value range for most mineral-bearing waters

6-9

"H+ is important in all reactions associated with the formation, alteration (direction of reaction) and dissolution of _________"

minerals

factors affecting pH in natural waters

biological activities (photosynthesis, respiration)


physical phenomena: aeration due to turbulence


minerals (e.g. dissoln / precip of CaCO3, because it can increase or decrease CO2 conc.)


oxygenation (often leads to decrease of pH)


denitrification and sulfate reduction (often leads to decrease in CO2)



bases in natural waters

Carbonate - CO3(2-)


Bicarbonate - HCO3(-)


Borate - B(OH)3 and its derivatives


Phosphate - PO4(3-)


Silicate - SO4(4-)


Ammonia - NH3


Arsenate - AsO3(-)

acids in natural waters

Sulfuric Acid - H2SO4


Nitric Acid - HNO3


Hydrochloric Acid - HCl


Ammonium - NH4(+)


Organic Acids

hydronium ion shape

Trigonal Pyramidal

true or false: pH is affected by ionic strength

true

density of seawater vs. freshwater


at 25C, in g/cm3

seawater: 1.02


freshwater: 1.0029

Freezing point of seawater vs. freshwater


in deg C

seawater: -1.91


freshwater: 0

Surface tension of seawater vs. freshwater


at 25C in dyne/cm

seawater: 72.72


freshwater: 71.97

water has a ______ boiling point and a _______ melting point

1. high


2. high

definition of hydrogen bond

electrostatic attraction that occurs between two polar molecules when a hydrogen bound to a highly electronegative atom such as N, F, or O experiences attraction to another highly electronegative atom

As temperature increases, hydrogen bonding _______

decreases

Explain the composite acid dissociation constant of H2CO3.

CO2 dissolves from atmosphere into ocean.


In ocean it hydrates to form H2CO3.


[H2CO3] and [CO2(aq)] indistinguishable


So we use a composite acid dissociation const, lumping the two quantities together.

pK(H2CO3) = ?

3.8

pK(H2CO3*) = ?




(and why is it unusual?)

6.3




high for such a strong acid, but that's because it's a composite constant for the dissolution AND hydration of CO2, but between those two forms it's only about 0.3% in the hydrated form

for H2CO3, the first (composite) dissociation constant H2CO3* = ?




(and what's the easier approximation?)

K1* = K(H2CO3) / (1 + K)




but K is on the order of 650, so approximation:




K1 ~ K(H2CO3) / K




K: constant for hydration of CO2(aq)


K(H2CO3): dissociation constant for H2CO3 itself

name the equations for all the K's in the reaction chain in the dissolution of CO2 into the ocean

K = CO2(aq) / H2CO3 (hydration of CO2)


K1 = [H+] [HCO3-] / [H2CO3*]


K(H2CO3) = [H+] [HCO3-] / [H2CO3] **


K2 = [H+] [CO32-] / [HCO3-]


Kw = [H+] [OH-]

Henry's Law

P / Kh = concentration




P = partial pressure


Kh = a constant that depends on solute, solvent, and temperature


concentration = concentration of gas in the liquid

Partial pressure

Pressure x (that gas's mole fraction)

Young-Dupre equation

W0 = gamma_lv (1 + cos a)




gamma_lv = force between liquid and gas




describes adhesion energy vs. contact angle

as contact angle decreases, adhesion ________

increases

interfacial energy of water and air (gamma_lv)

72 mJ/m2

surface energy

the energy required to break the bond between molecules at the surface (interface) between two fluids.




often expressed as gamma_(fluid1-fluid2)

Young's relation

cos a = (sg - sl) / lg




re: contact angle in terms of interfacial energies