ACIDS & BASES

Intro.  Write everything you know about the topic acids and bases

Acids Properties:

- form clear solutions that conduct electricity

(because the formation of the H⁺ frees up an electron * see dissociation equation)

- blue litmus paper turns pink

- phenolphthalein indicator is clear

- bromothymol indicator blue turns yellow

- pH is a code to measure how strong the acid or base is

Acids are pH 1 – 7, neutral water is 7

- pH paper turns orange

- universal indicator turns yellow.. orange,… red

- mild acids taste sour or tart (vinegar)

- acid stops bacteria from growing

- acids react with metals to ….

2HCl  +   Mg  à   H₂ (g)  +  MgCl_{2 (aq)      * Hydrogen pops when tested}

According to Arrhenius,  acids give up a H+ in water.

HCl  +  H₂O   à  H₃O⁺   +   Cl ^-  

                                        ^{Hydronium ion}

-  H₂O      - H₂O

_____________________________________________________

HCl                 à  H⁺   +   Cl ^-      Acid dissociation equation

HNO₃ à   H ⁺    +  NO₃^-

H₂SO₄ à   H ⁺    +  HSO₄^-

HSO₄^- à    H⁺     +  SO₄ ^2-

H₂CO₃ à   H⁺    +  HCO₃ ^-

H₂CO₃ à   2H⁺    +  CO₃ ^2-

H₂SO₄ à   2H ⁺    +  SO₄^2-

The concentration of the [H+] can be measured, and it gives a measure of the strength of the acid.

[H+] = 10 ^-1 M  (mol/L)  =  pH = 1   stronger acid

[H+]  = 10 ^-2 M              =  pH = 2    weaker acid

[H+] = 10 ^-7  M                    pH = 7     neutral

[H+] = 10 ^-9  M                    pH = 9     basic

1 =<  pH < 7 means acidic

The smaller the concentration of H+, the bigger the pH !

* Nitric acid + copper  demo

Naming Acids: (see handout)

First look at the ion that combined with the H to make the acid and find its name (on your ion sheet).

HCl … Cl ^1-   … “ide”   à Hydrochloric acid

HClO…  ClO ^1-  … hypochlorite…  à Hypochlorous acid

HClO₂  …ClO₂^1-   …. chlorite  ….  à  Chlorous acid

HClO₃…. ClO₃^1-    …. Chlorate    … à Chloric acid.

* Know some common acids to help you remember the rules

      Sulphuric acid      H₂SO₄

     Hydrochloric acid  HCl

BASES

- also known as alkali chemicals

- bitter, soapy, chalky tasting  (Tums, antacids..)

- neutralize acids

- strong bases attack organic “scum”  (Drano, toilet bowl cleaners)

React with water to form “hydroxides”

NaOH _(s)  +  H₂O  à  Na⁺   +  OH^-   +  H₂O

         NaOH     à  Na⁺   +  OH^-

name using the standard “hydroxide ending”