Exam Three Review

Glossary

100

Buffer

a solution that resists changes in pH when acid or base is added to it. Buffers typically involve a weak acid with it's conjugate base in comparable amounts

200

Titration

is a common laboratory method of quantitative chemical analysis to determine the concentration of an identified substance 

300

Third Law of Thermodynamics

The entropy of a perfect crystal at absolution zero (0 K) is zero  

400

Spontaneous

a process or reaction is one
that occurs (however slowly) without
continuous intervention

500

Closed System

Heat and work can flow through the system, but matter cannot come or leave

Formula

100

Henderson Hasselbach

pH= pKa + log [base]/[acid]

200

pH equivalence

pKa_(higher) + pKa_(lower)

                2

300

Entropy

S = k_b lnΩ 

400

Energy

∆E = q + W

500

Free Energy

∆G = ∆H - T∆S

Conceptual

100

What is pH when amounts of acid and conjugate base are equal?

pH = pKa of acid

200

To calculate pH of an amphoteric solution we use what equation?

pH equivalence  = pKa_(higher) + pKa_(lower)

                                           2

300

What's the difference between macro and micro states?

Macro state: different ways particles can be arranged (big picture)

Micro state: individual ways those particles can be arranged to get a macros state(possible combinations)

400

Describe Thermodynamics vs. Kinetics

Thermodynamics deals with whether a process
is spontaneous based on the energy difference
between initial and final states 

Kinetics deals with how fast a process will reach
equilibrium based on the energy of the pathway

500

Can Enthalpy predict spontaneity?

No, because both exothermic and endothermic processes can be spontaneous so Enthalpy is not a reliable indicator.

Quantitive

100

What is the pH of a solution containing 0.02 M HA and 0.01 M A-? pKa of HA = 5.0

What is the ICE table?

         HA     ->    H⁺   +    A^-

I       0.02M       0            0.01M

C          -x         +x          +x

E       0.02-x       x          0.01+x

200

What is the pH of a solution containing 0.02 M HA and 0.01 M A-? pKa of HA = 5.0

What is the x?

x=    2 * 10^-5 

300

What is the pH of a solution containing 0.02 M HA and 0.01 M A-? pKa of HA = 5.0

What is the pH?

pH= 4.7

400

A reaction occurs at 68 °F, the change in heat (delta H) = 19,070 J, and the change in entropy (delta S) = 90 J/K. 

What is Gibbs free energy? Spontaneous or no?

-7.3 kJ

Spontaneous

500

A reaction occurs at 68 °F, the change in heat (delta H) = 4,103 J, and the change in entropy (delta S) = 2.4 J/K.

What is Gibbs free energy? Spontaneous or no?

3.4 kJ

Nonspontaneous