CHEM 161 Exam 3

Arrhenius definition

substances behavior in water; involves H+; acid releases, base accepts

Bronsted-Lowry definition

based on proton transfer. Acid is proton donor, base is an acceptor and must contain a lone pair

is Kc greater than or less than 1 when a reaction proceeds to the right?

Kc>1

higher Ka = (in terms of acidity)

more acidic

write the equation for water autoionization

2H2O —> H3O + OH

write the expression for Kw

(OH)(H3O)=Kw (1×10^-14)

pKw=?

pH+pOH=14

What is the general rule for solving strong acid problems

[HA]=[A-] makes Kc=very large

What is the general rule for solving strong base problems

inital conc = final OH

How do you solve for pH and [H3O] of strong acids

conc equals initial and plug into -log(H3O)

formula for % HA dissociated

[HA] diss / [HA] init x 100

acid strength trends of nonmetal hydrides

1. acid strength increases down a group 2. acid strength increases across a period

acid strength trends of oxoacids

1. acid strength increases with # of O atoms 2. acid strenth increases with increasing EN of central nonmetal

how do hydrated metal ions work?

Small and highly charged metals can transfer H+ to H2O to form acidic solutions. For example, Mn and Al

What is the relationship between Ka, Kb, Kw

Ka x Kb= Kw

What is the relationship between pKa and pKb

pKa+pKb=14

what type of salts yield neutral solutions

cation of a strong base (ex:Na+) and an anion of a strong acid (ex:NO3-) because neither will react with water to a great extent

what type of salts yield an acidic solution?

a cation of a weak base (ex: NH4+) and and anion of a strong acid (ex: Cl-). Acidic because the weak base will react with water to form H3O+; a salt that has a small, highly charged metal cation and an anion of a strong acid because the hydrated metal will give their H+ to water.

Lewis Acid/bases

lewis acid accepts an electron pair. lewis base donates an electron pair

Buffer works through the ________ effect

common ion

How do acids and bases of a buffer function?

acid component neutralizes base and vise versa

why are they often conjugate acid-base pairs of weak acids?

The components of the pair don’t neutralize each other because they are conjugates.

whats the relationship between buffer range and buffer component ratio?

pKa +- 1

what is the henderson-hasselbalch equation

pH=pKa+log[A-/HA]

buffer capacity; what its dependent on

strength of the buffer; dependent on concentration of buffer components and relativity of buffer components to eachother

buffer range

pH range over which the buffer is effective. closer to 1=more effective.

How do you choose a buffer?

the pKa of the weak acid must me close to the desired pH

Qsp

ion-product constant for slightly soluble ionic compounds

when a common ion is added to a solution, what happens?

more precip forms

when two solutions of slightly soluble compounds mix under these circumstances what happens?

a) Qsp=Ksp

b) Qsp>Ksp

c) Qsp<Ksp

a) no change b)precipitate forms until remaining solution is saturated c) no precipitate will form. sol is unsaturated

is Ag(halide) soluble or insoluble

insoluble

are nitrates and group 1 soluble or insoluble

soluble

the concentration of any solid compound is ____

1

spontaneous change

occurs without any input of energy from outside system

S^o

standard molar entropy at 1 atm, 1 M, 298K

Entropy increases from these 5 things:

temp increases, loosening of physical state, increasing atomic size, increasing molecular complexity

how does entropy change after dissolution of a salt

increases

how does entropy change when ethanol dissolves in water

slight increase due to similar structure

what is gibbs free energy equation

delta G = delta H (sys) - T(delta S (sys))

what does G have to be for a spontaneous process to occur? for it not? at equilibrium?

less than zero, greater than zero, equal to zero.