1. CI 8.1 Acids and Bases

2. Acids  Turn litmus red  Neutralised by bases  pH < 7  Liberate CO 2 from carbonates

3. Br Ø nsted-Lowry Theory  An acid is an H + donor  A base is an H + acceptor  H + Cl - + NH 3  Cl - +NH 4 +

4. The oxonium ion  An acid reacts with water to form oxonium ions  HCl + H 2 O  H 3 O + + Cl -  Water is acting as a base

5. The oxonium ion H O H H+H+ x x What type of bond is this?

6. Is there a difference between an alkali and a base? A base is a substance which accepts H + ions Alkali = a base which forms OH - ions in water

7. How are hydroxide ions (OH - ) made?  NaOHNa + + OH -  CO 3 2- + H 2 OHCO 3 - + OH -  NH 3 + H 2 O NH 4 + + OH -

8. Acid – base pairs  CH 3 COOH CH 3 COO - + H +  CH 3 COO - + H + CH 3 COOH The ethanoate ion can behave as a base; it is the conjugate base of ethanoic acid.  HA H + +A - Conjugate acid Conjugate base

9.  Every acid has a conjugate base  Every base has a conjugate acid

10. Amphoteric substances  Water can act as either an acid or a base  With a strong acid it acts as a base  With a strong base it acts as an acid  A substance which behaves in this way is said to be amphoteric

11.  Water in the presence of a strong acid: H 3 O + H + + H 2 O  Water in the presence of a strong base: H 2 OH + + OH - Water as an amphoteric substance

12. Strength of acids and bases  A strong acid is a powerful H + donor; it is fully dissociated  A weak acid is a moderate or weak H + donor; it is weakly dissociated  A strong acid has a weak conjugate base and vice versa

13. Indicators  Coloured organic substances  Weak acids  Conjugate acid and conjugate base forms are different colours  e.g. litmus: HIn H + + In - red blue Which is the acid form?

14. Addition of acid  In - + H 3 O + HIn + H 2 O  The blue litmus turns red What is the equation for addition of alkali?