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Equilibrium

1.^

Molecular

------------------- Chapter 15

2.^

Ionic (Weak Acid / Base ) - Chapter 16

3.^

Ionic (“Insoluble” Salts)

- Chapter 17

STRONG

Acids & Bases

1.^

COMPLETELY IONIZED

1.^

COMPLETELY IONIZED

1.^

COMPLETELY IONIZED

1.^

COMPLETELY IONIZED (a)^

HCl(aq)

^

+^ H (aq)

+

Cl

-^ (aq)

(b)^

NaOH(aq)

^

+Na (aq) + OH

- (aq) 2.^

ONLY IONS PRESENT

2.^

ONLY IONS PRESENT

2.^

ONLY IONS PRESENT

2.^

ONLY IONS PRESENT + (a) H

(aq) & Cl

-^ (aq)

(b)^

+Na (aq) & OH

- (aq)

3.^

NO EQUILIBRIUM

3.^

NO EQUILIBRIUM

3.^

NO EQUILIBRIUM

3.^

NO EQUILIBRIUM

The [H] of 0.

M^

HCN(aq) is?

{K

= 4.9 x 10a

What do you do 1

st^?

ST 1

Write & Balance “Reaction” HCN(aq)

+ H

(aq) + CN

-^ (aq)

nd^2 Write Equilibrium Expression

]

[

]

][

[H

CN HCN

Ka

−

Initial

Change

Equilibrium

Find [H] of 0.

M^

HCN

K= 4.9 x 10a^

HCN(aq)

+ H

(aq) + CN

-^ (aq)

I^ NITIALNITIALNITIALNITIAL

C^ HANGEHANGEHANGEHANGE

-^

x^

+^ x

+^ x

E^ QUILIBRIUMQUILIBRIUMQUILIBRIUMQUILIBRIUM

0.5 – x

x + 0

x + 0

What approximation?

Yes!!Why?

Since

x^ ≅

1.6 x 10

-^

is so small

0.50 - x

x 0.5x = 0.

x 0.

2 2

pH – A measure of Acidity

The pH of a solution is defined as

the

negative logarithm of the hydrogen ion

concentration (in mol/L)

.

pH = –log [H

+]

pOH = –log [OH

• ]

pH + pOH = 14

Definitions of Acids & Bases

1. Arrhenius2. Bronsted-Lowry3. Lewis

Acid / Base

ACIDACIDACIDACID

:^ A substance which dissociates to form hydronium ions (H

+O 3

) in solution :

HA(

aq )

+ H

( aq

) + A

• ( aq

BASEBASEBASEBASE

:^ A substance that dissociates to form hydroxide ions (OH

• ) in solution :

MOH(

aq )

+ M

( aq

) + OH

• ( aq

M = a Metal

LEWISLEWISLEWIS

Acid / Base

-^ Acid

is an

electron-pair acceptor

.^ These are

generally cations and neutral molecules withvacant valence orbitals. For example H

+^ & BF

. 3 -^ Base

is an

electron-pair donor

. These are

generally anions and neutral molecules withavailable pairs of electrons, such as H

O, NH 2

, O 3 2–

-^ The bond formed is called a

coordinate bond

STRENGTH OF ACIDS AND BASESSTRENGTH OF ACIDS AND BASESSTRENGTH OF ACIDS AND BASES HCl(aq) is a strong acid but Cl

-^ is a “weak” base

Why?

Because Cl

-^ will not react with H

Why Not?

If it did, HCl(aq) {a strong acid} would form

which does not exist

STRENGTH OF ACIDS AND BASESSTRENGTH OF ACIDS AND BASESSTRENGTH OF ACIDS AND BASES HClO

4 HI HBrHClHNO

3

HFHNO

2 HCOOHNH

• 4 HCNHO^2

ClO

• 4

  • I Br^

    Cl^ 

NO

• 3

– F NO

• 2 HCOO

NH

3 CN

• OH

ACID

BASE

ACID

BASE

Increasing Acid Strength

Strong Acids

• BASE PAIRS

An Acid and a Base thatdiffer only in the presence^ {or absence}

of a proton.

• BASE PAIRS

HClO

4 HI HBrHClHSO^2

4 HNO

3 HO^3

HSO

• 4

HSO

• 4 HFHNO

2 HCOOHNH

• 4 HCNHO^2 NH

3

ClO

• 4
  • I – Br^ – Cl^ HSO
    • 4 NO
• 3 HO^2 SO

2– 4

SO

2– 4

• F (^) NO
  • 2 HCOO

NH

3 CN

• OH

NH

• 2

ACID

CONJ. BASE

ACID

CONJ. BASE

What are the conjugate bases of the following

Brønsted–Lowry acids

HSO^2

4 HClO

4 HSO^2

4 HSO

– 4 HO 2

+ H

O^2

^

HO^3

+^ + HSO

• 4

+ H

O^2

+ H

O^2

+ H

O^2

+ H

O^2