CHM2046 Exam 1 Review

The stronger the acid…

the weaker the conjugate base.

Describe the relationship between Lewis acids and bases and Bronsted-Lowry acids and bases.

B-L definition is a subset of Lewis definition.

Lewis acid

Accepts an electron pair to form a bond

Lewis base

Donates an electron pair to form a bond

The Lewis definition does not expand the classes of ___, but it does greatly expand the classes of ___.

Doesn’t expand bases, does expand acids

The product of a Lewis acid-base reaction

Adduct

Adduct

The product of a Lewis acid-base reaction, a species that contains a new covalent bond

The most important of the electron-deficient lewis acids are

compounds of group 13 elements boron and aluminum

Species that act as Lewis acids

Arrhenius acids, Bronsted-Lowry acids, and:

-Electron-deficient molecules

-Molecules with polar multiple bonds

-Metal cations

Kw =

[H3O+][OH-] = 1.0 × 10^-14 at 25 C

In pure water, [H3O+] =

[OH-] = 1.0 × 10^-7

pKw =

pH + pOH = 14.00

pH =

-log[H3O+]

pOH =

-log[OH-]

A reaction proceeds to the greater extent in the direction in which…

a stronger acid and stronger base form a weaker acid and weaker base.

When comparing the same central atom, acidity increases with…

#O atoms

Salt hydrolysis questions

Strong acid + strong base = neutral

Where does Kc come from?

kfwd[A] = krev[B] → kf/kr = [B]/[A] = Kc

Why do chemical reactions not go to completion?

All reactions are reversible.

Only __ can change the value of K.

temperature

In an endothermic reaction, equilibrium likely lies ___. Why?

Left, because the rxn requires energy to proceed.

In an exothermic reaction, equilibrium likely lies ___. Why?

Right, because the rxn releases energy as it proceeds.

Changes to equilibrium

-Concentration of reactants or products

-Pressure/volume

-Temperature

Ways to change pressure and how they affect equilibrium:

1. Change in P of one gas involved in the reaction: Q → K

2. Addition of an inert gas (one not involved in the reaction): Partial pressures stay the same, so Q stays the same. No change to equilibrium.

3. Change in the volume of the vessel: Decrease V shifts to less moles of gas. Increase volume shifts to more morles of gas.

Do catalysts affect K? Why or why not?

No, catalysts don’t affect K. They speed up the rate of reaction both forward and reverse.

Give the equation and ways to maximize product yield for the Haber-Bosch process.

N2 (g) + 3H2 (g) ⇌ 2NH3 (g) (exothermic)

-Increase concentration of N2 or H2

-Decrease temperature

-Decrease [NH3] by condensation

-Decrease volume

-Increase speed with catalyst

Arrhenius equation

Name the strong acids

HCl, HBr, HI, H2SO4, HClO4, HNO3

Name the strong bases

MOH, MO, M2O, M(OH)2, MS, M2S, M3S

In strong acid dissociations, [H3O+] =

[strong acid] x molar ratio

In strong base dissociations, [OH-] =

[strong base] x molar ratio

Write out the weak acid dissociation reaction

Stronger acids have __ pKa.

Lower

Draw H2SO3

Draw C6H5CH2COOH

Write out the weak base dissociation reaction

Most weak bases have ___.

an N atom with a lone pair

% HA dissociation =

As initial acid concentration decreases,

the percent dissociation of the acid increases.

____ can be acidic.

Highly charged metal cations

A salt with the conjugate acid of a strong base and the conjugate base of a strong acid gives ___ solution.

neutral

Conjugate base of a strong acid and conjugate acid of a weak base =

acidic solution

M^n+ ions give ___ solution

acidic

NaHSO4 in solution

acidic

Conjugate base of a weak acid and conjugate acid of a strong base give __ solution.

basic

CO2 (aq) is a Lewis ___.

acid

Factors that affect the acidity of nonmetal hydrides

1. Electronegativity (across a period)

2. Atom size (bond strength) down a group

Factors that affect the acidity of oxoacids

1. When comparing similar structures, electronegativity (more = more acidic)

2. When comparing same central atom, # oxo groups (more = more acidic)

For a gas mixture, volume fraction = ___.

mole fraction

Which of the following statement(s) is/are true about the autoionization of water?

a. In the autoionization process, water acts as both acid and base.

b. When a strong acid is added to water, water autoionization is suppressed and the

equilibrium shifts to the left.

c. When a strong acid is added to water, the water autoionization equilibrium is not affected,

since Kw is constant.

d. No matter how the temperature changes, the pH of pure water will always be 7.

a and b