Chemistry Of Water

Front 1

Arrhenius acid

Back 1

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

Front 2

Arrhenius base

Back 2

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

Front 3

Common Arrhenius bases

Back 3

Group 1 and 2 cations

Front 4

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

Back 4

Arrhenius acid + Arrhenius base --> water + salt

Front 5

Limitations of Arrhenius definition

Back 5

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

Front 6

pH

Back 6

-log[H+]

Front 7

pOH

Back 7

-log[OH-]

Front 8

[H+]

Back 8

10^(-pH)

Front 9

[OH-]

Back 9

10^(-pOH)

Front 10

pH + pOH = ?

(for any aqueous solution at T = 25C)

Back 10

14

Front 11

The two properties of an acid solution that determine pH

Back 11

strength and concentration

Front 12

strong acid/base

Back 12

one that dissociates completely in water

Front 13

Bronsted-Lowry acid

Back 13

a species which is capable of donating a proton

Front 14

Bronsted-Lowry base

Back 14

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

Front 15

amphoteric

Back 15

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

usually used in reference to water.

Front 16

Strong acids/bases ionize/dissociate _____

Back 16

completely

Front 17

Weak acids/bases ionize/dissociate _____

Back 17

only partially

Front 18

Conjugate base of a Bronsted-Lowry acid

Back 18

the species formed after the acid has donated its proton

Front 19

Conjugate acid of a Bronsted-Lowry base

Back 19

the species formed after the base has accepted a proton

Front 20

Common strong acids

(there are 6 of them)

Back 20

HCl (hydrochloric acid)

HBr (hydrobromic acid)

HI (hydroiodic acid)

H2SO4 (sulfuric acid)

HNO3 (nitric acid)

HClO4 (perchloric acid)

Front 21

Common strong bases

Back 21

Group 1 and 2 hydroxides

Front 22

Common weak bases

Back 22

neutral nitrogen-containing compounds, e.g.

ammonia NH3

trimethylamine N(CH3)3

pyridine C5H5N

Front 23

pKw at T = 25C

Back 23

14

Front 24

Kw at T = 25C

Back 24

1 x 10^(-14)

Front 25

pKw in terms of pH and pOH

Back 25

pKw = pH + pOH

Front 26

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

Back 26

Kw = [H3O+][OH-]

Front 27

Number of mol of water in a liter

Back 27

56

Front 28

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

Back 28

1 to 560,000,000

Front 29

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

Back 29

weak acids and weak bases

Front 30

Ka

Back 30

acid dissociation constant.

equilibrium constant for the equation:

HA + H2O --> A- + H3O+

Front 31

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

Back 31

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

Front 32

Kw in terms of Ka and Kb

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

Back 32

Kw = Ka * Kb

Front 33

Kb

Back 33

the base association constant.

the analog of Ka but for bases.

Equilibrium constant for the equation:

B + H2O <-> HB+ + OH-

Front 34

pKw in terms of pKa and pKb

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

Back 34

pKw = pKa + pKb

Front 35

A strong acid's conjugate base is ______ in water

Back 35

neutral

Front 36

A weak acid's conjugate base is a ____ base

A weak base's conjugate acid is a ____ acid

Back 36

1. weak

2. weak

Front 37

For a strong acid, Ka ____ 1

Back 37

Ka >> 1

Front 38

Equation for Kb

Back 38

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

Front 39

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

Back 39

basic

Front 40

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

Back 40

acidic

Front 41

Effect of temperature on pKw

Back 41

As temperature increases, pKw decreases

(i.e. Kw increases)

Front 42

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

Back 42

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.

Front 43

Correction for activity of free ion a_i

Back 43

ai = m_i * gamma_i

m_i = mass fraction

gamma_i = activity coefficient

Front 44

Ionic Strength:

what is the equation and what are the units?

Back 44

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

...where _i refers to the ith ion

ionic strength has concentration units

Front 45

Hydration

Back 45

when an ion is surrounded and stabilized by water molecules

Front 46

spectator ions

Back 46

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

Front 47

formula for solubility product constant

Back 47

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

e.g. for salt:

Ksp = [Na+][Cl-]

Front 48

effect of pressure on solubility of a gas

Back 48

increase in pressure means increase of solubility for the gas

Front 49

effect of pressure on solubility of solid or liquid

Back 49

no effect

Front 50

true/false: pH affects solubility?

Back 50

true.

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

Front 51

effect of ionic strength on solubility

Back 51

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?)

Front 52

dissolution vs. solubility

Back 52

solubility is a thermodynamic concept

dissolution is a kinetic concept

Front 53

pH value range for most mineral-bearing waters

Back 53

6-9

Front 54

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

Back 54

minerals

Front 55

factors affecting pH in natural waters

Back 55

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)

Front 56

bases in natural waters

Back 56

Carbonate - CO3(2-)

Bicarbonate - HCO3(-)

Borate - B(OH)3 and its derivatives

Phosphate - PO4(3-)

Silicate - SO4(4-)

Ammonia - NH3

Arsenate - AsO3(-)

Front 57

acids in natural waters

Back 57

Sulfuric Acid - H2SO4

Nitric Acid - HNO3

Hydrochloric Acid - HCl

Ammonium - NH4(+)

Organic Acids

Front 58

hydronium ion shape

Back 58

Trigonal Pyramidal

Front 59

true or false: pH is affected by ionic strength

Back 59

true

Front 60

density of seawater vs. freshwater

at 25C, in g/cm3

Back 60

seawater: 1.02

freshwater: 1.0029

Front 61

Freezing point of seawater vs. freshwater

in deg C

Back 61

seawater: -1.91

freshwater: 0

Front 62

Surface tension of seawater vs. freshwater

at 25C in dyne/cm

Back 62

seawater: 72.72

freshwater: 71.97

Front 63

water has a ______ boiling point and a _______ melting point

Back 63

1. high

2. high

Front 64

definition of hydrogen bond

Back 64

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

Front 65

As temperature increases, hydrogen bonding _______

Back 65

decreases

Front 66

Explain the composite acid dissociation constant of H2CO3.

Back 66

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.

Front 67

pK(H2CO3) = ?

Back 67

3.8

Front 68

pK(H2CO3*) = ?

(and why is it unusual?)

Back 68

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

Front 69

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

(and what's the easier approximation?)

Back 69

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

Front 70

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

Back 70

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

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

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

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

Kw = [H+] [OH-]

Front 71

Henry's Law

Back 71

P / Kh = concentration

P = partial pressure

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

concentration = concentration of gas in the liquid

Front 72

Partial pressure

Back 72

Pressure x (that gas's mole fraction)

Front 73

Young-Dupre equation

Back 73

W0 = gamma_lv (1 + cos a)

gamma_lv = force between liquid and gas

describes adhesion energy vs. contact angle

Front 74

as contact angle decreases, adhesion ________

Back 74

increases

Front 75

interfacial energy of water and air (gamma_lv)

Back 75

72 mJ/m2

Front 76

surface energy

Back 76

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

often expressed as gamma_(fluid1-fluid2)

Front 77

Young's relation

Back 77

cos a = (sg - sl) / lg

re: contact angle in terms of interfacial energies