in the case of NaOH and HC1, why are the normality and molarity the same?

Answer 1

Normality is essentially just the molarity multiplied by the number of times a molecule can participate in a reaction.

So, since NaOH can only adsorb a single proton, and HCl can only donate a single proton, their molarity is the same as their normality.

H2SO4 is a diprotic acid, and therefore its normality is twice its molarity. (since it can donate two protons.)

Consequently, Na2SO4 is a base which would have twice the normality of its molarity, since it can adsorb two protons per [SO4]2- ion.

Answer 2

Normality refers to the concentration of the H+ or OH- ion, while molarity is the concentration of the whole compound. In the case of NaOH and HCl, each compound has only one H or OH, so when it dissociates, the concentration of the H and OH is the same as the original compound. In an acid like H2SO4, for example, there are two H+ ions for each H2SO4 molecule, so the normality would be 2X the molarity.