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Acids & Bases

K Warne

WEAK STRONG

[H3O+]

(mol/dm3)

Log [H3O+]

pH= -

log[H3O+]0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

B A S E SA C I D S W A T E RWEAKSTRONG NEUTRAL

1 0.1 0.01 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14

0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 12 -13 -14

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Acid strength & pH

H3O+ concentration (mol/dm3)

1 0.01 0.001

Strong acids Weak acids

0.0001 0.000001

(1x10-4) (1x10-5)

Diluting a strong acid by a factor of ten changes

its pH by one unit.

pH = - log10[H3O+]

WEAK STRONG

[H3O+]

(mol/dm3)

Log [H3O+]

pH= -

log[H3O+]0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

B A S E SA C I D S W A T E RWEAKSTRONG NEUTRAL

1 0.1 0.01 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14

0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 -11 12 -13 -14

2

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Acids - IonisationAll acids ……………..in solution to give ….. ions.

HCl H+ + Cl- (100%)

HCl (+ H2O) ………(aq) + Cl-(aq)

H2O + H+ ………

Nitric Acid: HNO3 …… + NO3- (nitrate anion)

Sulphuric Acid: H2SO4 …… + SO42- (sulphate anion)

Carbonic Acid: H2CO3 …… + CO32- (carbonate anion)

Ethanoic acid: CH3COOH …… + CH3COO-

(ethanoate anion)

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Acids - IonisationAll acids ionise in solution to give H+ ions.

HCl H+ + Cl- (100%)

HCl (+ H2O) H3O+

(aq) + Cl-(aq)

H2O + H+ H3O

+

Nitric Acid: HNO3 H+ + NO3- (nitrate anion)

Sulphuric Acid: H2SO4 2H+ + SO42- (sulphate anion)

Carbonic Acid: H2CO3 2H+ + CO32- (carbonate anion)

Ethanoic acid: CH3COOH H+ + CH3COO-

(ethanoate anion)

4

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SALTS A SALT is a compound formed when a metal is ionically bonded to a

non-metal.

Salts are formed in many acid-base reactions.

Acid + Metal SALT + hydrogen

Acid + Metal Oxide SALT + water

Acid + Metal hydroxide SALT + water

Acid + Metal carbonate SALT + carbon dioxide + water

Acid + Metal hydrogen carbonate SALT + carbon dioxide + water

SALT ACID BASE ACID BASE SALT

MgCl2 HCL Mg HCl Mg(OH)2 MgCl2

Fe(NO3)2 HNO3 Fe(OH)2 H2SO3 NaOH Na2SO3

MgCO3 H2 CO3 MgO H2CO3 CaO CaCO3

Al2 (SO4 )3 H2 SO4 Al(OH)3 H2CO3 CaCO3 CaCO3

(NH4)3 PO4 H3PO4 NH3 H2SO4 Mg MgSO4.SAMPLE ONLY SAMPLE ONLY 5

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Cl-

Acids - ionisation

2

H+

H+

H+Cl-

Cl-

Cl-

H+

H+Cl-

Cl-

20 HCl

Dilute Strong acid

• all molecules

dissociated

• few molecules / dm3.

Concentrated Strong Acid:

•All molecules dissociated

•Many molecules per dm3

H Cl

H+Cl-

Cl-

Cl- Cl-

H+

H+

H+

H+

H+H+

H+

H+

H+

H+

H+H+H+

Cl-

Cl-Cl-

Cl-

Cl-

H Cl

6

pH calculations 1 Equations

pH = -log10[H+] [H+] = 10-pH

Example:

Calculate the pH for a specific [H+]: Given [H+] = 1.4 x 10-5 M

pH = log10[H+]

= log10(1.4 x 10-5)

= 4.85

Calculate the [H+] from pH: Given pH = 3.5

[H+] = 10-pH

= 10-3.5

= 3.16 x 10-4 mol.dm-3

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Hi -

This is a SAMPLE presentation only.

My FULL presentations, which contain a lot more more slides and other resources, are freely

available on my resource sharing website:

www.warnescience.net(click on link or logo)

Have a look and enjoy!

WarneScience