2. Hi guys! My name is Lyecid and I’m gonna help you to discover acids and bases.

3. What are acids and bases? Who got interested in acids and bases? What is pH scale?

4. Electrolytes are substances able to conduct electricity in water. HOME

5. MeOH Me (aq) + + OH (aq) - H2OH2O HX H (aq) + + X (aq) - H2OH2O A lot of people got interested in acids and bases, but for most of time they couldn’t find an accurate definition. The first scientist who worked out a theory about acids and bases was Arrhenius. S.A. Arrhenius HOME

6. This theory was limited to water and didn’t explain other substance behaviour. So two scientists, Brönsted e Lowry,created a new theory. HX + : B X - + BH + HOME

7. Being more general, this theory is about the reaction between an acid and a base Bronsted and Lowry introduced the concept of conjugated couples. HX + : B X - + BH + ACIDBASE CONJUGATED BASECONJUGATED ACID HOME

8. Now let’s focus our attention on water As you can see, water behaves as acid or base depending on the substance it reacts with. This kind of subastances are called amphoteric. HOME

9. Then another scientist, Lewis elaborated another theory, more general than previous ones HOME

10. pH scale measures how acidic or basic a solution is and goes from 0 to 14. pH can be measured by a specific instrument or by litmus. HOME

11. In order to calculate pH value, we have to consider two different categories: strong and weak acids or bases. Weak acids are those which don’t ionize completely, releasing only a part of H⁺ ions they have. An example of weak acid is acetic acid. Let’s see its behaviour: Strong ones ionize completely, releasing nearly all the hydronium ions it has. An example of this kind of acids is hydrochloric acid: HOME

12. To recognise a strong or a weak acid, the acid dissociation constant has been introduced and it comes from the law of mass action. HX + : B X - + BH + It’s used for weak acids, being about chemical equilibrium. Kₐ= HOME

13. For a strong acid the molarity of H₃O⁺ is the same as the starting acid concentration. STRONG ACID WEAK ACID pH = -log [C ₐ ] pH = -log [H₃O⁺]=[X⁻], our unknown quantity [H₃O⁺]²= Kₐ Cₐ