PROPERTIES OF ACIDS AND BASES

Acids• taste sour or tart (vinegar, lemons)• aqueous solutions of acids are electrolytes• cause indicators to change colors• many metals react with acids to produce H2

gas• react with hydroxides to form a salt and

water• most formulas begin with H.• pH < 7, pOH > 7• [H3O+] > 1.0 x 10-7, [OH-] < 1.0 x 10-7

• produce H3O+ (aka H+) ions in water solutions

Common uses of acids

• HNO3 or HCl are used for etching metals.

• HF is used for etching glass.

Bases

• bitter taste (soap, unsweetened chocolate)

• bases are electrolytes in aqueous solution• cause indicators to change colors• feel slippery• react with acids to form a salt and water• often contain OH- , or ammonia NH3 • pH > 7, pOH < 7• [H3O+] < 1.0 x 10-7, [OH-] > 1.0 x 10-7

• produce OH- ions in water solutions

• hydroxide ion (OH-) – formed when a water molecule loses a H+

• hydronium ion (H3O+)

– formed when a water molecule gains a H+

H2O + H+ H3O+

*your text uses H+ and H3O+ interchangeably*

Acidic solutions

[H3O+] > [OH-]

[H3O+] > 1.0 x 10-7

Basic solutions

[OH-] > [H3O+]

[OH-] > 1.0 x 10-7

[H3O+] < 1.0 x 10-7

Acidic or Basic?

• [H3O+] = 1 x 10-3

• [H3O+] = 1 x 10-11

• [OH-] = 1 x 10-4

• [OH-] = 1 x 10-13

H+ > 1.0 x 10-7

H+ < 1.0 x 10-7

OH- > 1.0 x 10-7

OH- < 1.0 x 10-7

Acidic

Basic

Basic

Acidic

[H3O+] = 1 x 10-10

[H3O+] = 1 x 10-1

pH Concept:

pH = - log [H3O+] or - log [H+]

In calculator enter:- log (value)

Example:

If [H3O+] = 1.0 x 10-4

pH = - log [H3O+]

then pH = -log [1.0 x 10-4]

= 4.00

pH problems:

What is the pH if:

[H3O+] = 1 x 10-5 pH = __________

pH = - log [H3O+]

[H3O+] = 1 x 10-13 pH = __________

pH = - log [H3O+]

pH > 7 is basicpH < 7 is acidicpH = 7 is neutral

5

13

Acidic

Basic

pOH = -log [OH-]

What is the pOH if:[OH-] = 1 x 10-4 pOH =

pOH = -log [OH-][OH-] = 1 x 10-3 pOH =

pOH = -log [OH-]

4

3

Basic

Basic

pH + pOH = 14

pH = 6 pOH =

pH = 4 pOH =

pOH = 3 pH =

pOH = 11 pH =

8

1011

3

[H3O+] = antilog (-pH)[OH-] = antilog (-pOH)

• pH = 7.00 so [H3O+] =

[H3O+] = 10-7.00

• pH = 3.00 [H3O+] =

[H3O+] = 10-3.00

• pOH = 8.00 [OH-] =

[H3O+] =

[OH-] = 10-8.00

14 = 8 + x x = 6

[H3O+] = 10-pH

[OH-] = 10-pOH

1.00 x 10-3

1.00 x 10-8

1.00 x 10-6

1.00 x 10-7

Using a programmable calculator for pH:

What is the pH if [H3O+] = 5.2 x 10-2

pH = - log (H3O+)

pH = (-) log (5.2 x 10-2)

- log10 (5.2 x10-2) enter

pH =1.3

Using a programmable calculator for antilogs:

What is the [H3O+] if the pH is 4.92? [H3O+] = antilog (-pH) [H3O+] = antilog (-4.92)

Calculator:10x (- 4.92) Enter

[H3O+] =

10x is the 2nd function of the log key

1.20 x 10-5

Example:

• pH = 9.29 [H3O+] = ?

• [H3O+] = antilog (-pH)

• [H3O+] = antilog (-9.29)

• Calculator:

• 10x(-9.29) Enter

• [H3O+] = 5.13 x 10-10

ACIDS & BASES WORKSHEET IS

DUE

Indicators

• Indicators are substances that change color in solutions of different pH.

• Indicators are usually weak acids.

• They are one color in their acid form and a different color in their base form.

• HIn H+ + In-

• Help determine approximate pH

Indicators cont.

phenolphthalein

• colorless in acid

• pink in base

• changes at pH 8.0 -10.0

Indicators cont.

litmus• blue litmus turns red in acid• red turns blue in base

universal indicator• mixture of indicators• changes into different colors at each

pH (rainbow colors)

Indicators cont.

bromothymol blue

• blue in basic solutions

• yellow in acidic solutions

• green in neutral solutions

Common acids Common bases

HCl NaOH

HNO3 KOH

H2SO4 Ca(OH)2

H3PO4 Mg(OH)2

HC2H3O2 NH3

H2CO3

Acid-Base Reactions

• When acids and bases react, the products most commonly formed are water and a salt (ionic compound).

• This is called a neutralization reaction.