CHEM 1040 Forbes Exam 3 Review

Common-ion effect

a decrease in the solubility of an ionic compound caused by the addition of a common ion

Henderson-Hasselbalch equation

pH = pKa + log [A-]/[HA]

When [A-] = [HA], then

pH = pKa

When [A-] > [HA], then

pH > pKa

When [A-] < [HA], then

pH < pKa

What is a buffer solution?

A system that resists pH changes when small amounts of an acid or a base are added

Steps to solve buffer problems

Stoichiometry table, then either ICE tables or HH equation

Buffer capacity

the amount of acid or base that can be added without causing a large change in pH

Buffer systems are most effective when concentrations are high/low

high

A buffer becomes less effective as the difference in ___ increases

concentration

An effective buffer must have a base:acid range of

0.10-10

The more concentrated the buffer components, the more...

effective the buffer

The effective range for a buffering system is

one pH unit on either side of pKa

Buffer capacity increases/decreased with increasing/decreasing concentrations of buffer components

increases; increasing

The overall buffer capacity increases/decreases as the ratio of buffer components gets closer to ___

increases; 1

Titration

when a substance in a solution of known concentration is reacted with another substance in a solution of unknown concentration

Titration curve

a plot of the pH of a solution as a function of the volume of titrant added

Strong Acid - Strong Base Titration Curve

Equivalence point is 7

Weak Acid - Strong Base Titration Curve

Equivalence point is greater than 7, has a halfway equivalence point

Weak Base - Strong Acid Titration Curve

Equivalence point is less than 7

Solubility product constant (Ksp) formula

Equals the product of the concentrations of the ions each raised to a power equal to the coefficient of the ion in the dissociation equation

Precipitation reaction

occurs when two aqueous solutions containing ionic compounds are mixed and one of the products is insoluble

If Q = Ksp, the solution is

saturated

If Q < Ksp, the solution is

unsaturated

If Q > Ksp, the solution is

supersaturated

_______ tend to be good electron acceptors, which makes them a good ___ acid

Transition metals; Lewis acid

Most common Lewis bases that increase the solubility of metal cations are

NH3, CN-, and OH-

6 Strong Acids

HCl, HBr, HI, HNO3, H2SO4, HClO4

6 Strong Bases

LiOH, NaOH, KOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

Spontaneous process

a process that proceeds without outside intervention

Nonspontaneous process

a process that requires continuous outside intervention

Not all spontaneous processes are

self-starting, fast, and exothermic

The nonspontaneous formation of solid ice from liquid water is due to...

the restriction of the freedom of motion of the molecules

Decrease temperature, increase/decrease in freedom of motion

decrease; this makes the reaction spontaneous

What are the three types of freedom of motion for liquids and gases?

vibrational, rotational, and translational

Whenever an isolated thermodynamic system undergoes a change in which the particles in the system disperse into a larger volume and/or gain freedom, the process is always ____ and the system is said to have an increase in ____

spontaneous; entropy

Entropy formula (STATE function)

△Sfinal -- △Sintial

Entropy definition

measure of energy dispersal

Substances that are mixable will mix with each other spontaneously because....

there is a higher probability of a mixed distribution

The most probable mixing pattern produces...

a uniform distribution of particles throughout the volume they occupy

Increase in disorder, increase/decrease in entropy

increase

Entropy formula

S = klnW

Accessible microstates

Probable number of arrangements of particles in a system at a given temperature

Macrostate

overall state of the system defined by a set of conditions

Microstate

snapshot of a system at an instant in time

Absolute entropy

a crystalline solid in their lowest possible energy state (zero) only has one microstate

Standard molar entropy

the entropy value for a mole of a substance in its standard state

Larger mass, larger/smaller the entropy

larger

Entropy has a larger increases between ___ and ___ than solids and liquids

liquids and gases; this is due to molecular dispersion

Heating a substance at higher temperatures produce a smaller entropy increase than...

adding the same quantity of heat at a lower temperautre

Entropy increases with what three variables?

temperature, volume, and number of atoms

Entropy formula for state change at equilibrium

ΔS = qrev/T

If the ΔSuniv > 0, then a process is

spontaneous

If the ΔSuniv < 0, then a process is

nonspontaneous

ΔSsurr formula

ΔS = -ΔHsys/T

A process that emits heat into surroundings increases/decreases the entropy

increases

A process that absorbs heat from the surroundings increases/decreases the entropy

decreases

The magnitude of the change in entropy is _____ to the magnitude of ΔHsys

proportional

ΔSuniv formula

ΔSsys - ΔHsys/T

Gibbs free energy (G)

amount of energy available to do work

ΔGsys formula

-TΔSuniv

ΔG formula

ΔH - TΔS

ΔG is proportional to the positive/negative sign of ΔSuniv

negative

A decrease in Gibbs free energy corresponds to a ___ process

spontaneous

An increase in Gibbs free energy corresponds to a ___ process

nonspontaneous

ΔG formula under standard conditions

ΔHrxn - TΔSrxn

ΔG formula at thermodynamic equlibrium

ΔGstd + RTlnQ

Redox reaction

a type of chemical reaction that involves a transfer of electrons between two species

Balancing Chemical Equations in Neutral Solution Steps:

1. Separate into half reactions

2. Neutralize charges with e-

3. Scale the reactions so the number of electrons are equal

4. Add equations together and net ionic equation

Balancing Chemical Equations in Acidic Solution Steps:

1. Separate into half reactions

2. Balance elements other than O and H

3. Add water to balance O, add H+ to balance H

4. Balance charges with e-

5. Scale reactions so the number of e- are equal

6. Add equations together and get net ionic equations

Balancing Chemical Equations in Basic Solution Steps:

1. Separate into half reactions

2. Balance elements other than O and H

3. Add water to balance O, add H+ to balance H

4. Balance charges with e-

5. Scale reactions so the number of e- are equal

6. Cancel e-

7. Add OH- to balance H+

8. Combine OH and H+ to form water

9. Cancel common terms

Electrical current

flow of electric charge

Voltaic cell

an electrochemical cell that produces electrical current from a spontaneous reaction