Mini review for midterm 2

NB: This does not cover all material!

• Units, Conversions, Powers of 10, Prefixes• Errors: Sig Figs, Error propagation• Statistics: Normal distribution,

t-test, Q-test• Equilibrium: Constant, Ksp, KH, Kw,

separation by precipitation,acids & bases

• Titration: ve

(very) Rough outlinePart 1

See midterm 1 review

• Acids & bases - buffers• Acid-base titrations• Spectrophotometry Beer’s Law

Properties of lightAtomic spectroscopy

(very) Rough outlineFor Part 1

See midterm 1 review

EQUILIBRIUM

NB:K = f(T)K ≠ f(concentartions)

SOLUBILITY PRODUCT Ksp

COMMON ION EFFECT

Ksp = [Ca2+]3[PO43-]2 = 1.0 x 10-26

= (3x)3(0.10 + 2x)2 = 1.0 x 10-26

EQUILIBRIUM

x solubility (mols/L of Ca3(PO4) that can disolve)

TITRATION

STEP 1: reaction

STEP 2: Ve

STEP 4: at equivalence

STEP 5: after equivalence

STOICH

IOMETR

Y!

STEP 3: before equivalencewhat part is left?

all analyte consumed

excess titrant

ACTIVITY

SOLUBILITY PRODUCT Ksp

GAS SOLUTION KH

WATER KW

ACID Ka

BASE Kb

EQUILIBRIUM

WATER EQUILIBRIUM Kw

pH

EQUILIBRIUM

ACID – BASE EQUILIBRIUM

BUFFERS

NB:Equal concentrations pH = pKa

(most effective buffer)

Weak acidWith Strong base

HA H+ + A-

STEP 1: reaction

STEP 2: Ve

# mols base added = # mols acid removed

Weak acidWith Strong baseSTEP 3: before equivalence

BUFFER! HA H+ + A-

NB: at v = ve/2 concentrations are equal pH = pKa !

Weak acidWith Strong baseSTEP 3: before equivalence

BUFFER!STEP 4: at equivalence

A- + H2O HA + OH- Kb

HA H+ + A-

NB: What is pH at equivalence:for titration of strong acid with strong base?and for a weak acid with a strong base > or < 7?

Weak acidWith Strong baseSTEP 3: before equivalence

BUFFER!STEP 4: at equivalence

A- + H2O HA + OH- Kb

STEP 5: after equivalence

excess OH-

HA H+ + A-

Transmittance

Absorbance

Beer’s Law

Spectrophotometry

Spectrophotometry

ε depends on• molecule• wavelength

Spectrophotometry

λν = c [3 x 108 m/s]

E = h ν

Spectrophotometry

The fraction of atoms in the excited state is still less than 0.02%,but that fraction has increased by 100(1.74 – 1.67)/1.67 = 4%

Linewidth