Final answer:
To calculate the number of reactive protons in an unknown acid, one needs to determine the acid's structure or use titration. The mole:mole ratio and stoichiometric coefficients in the reaction's balanced equation indicate the proportion of reactants to products. Titrations help calculate the molarity of an unknown acid solution by using a standard solution of a strong base.
Step-by-step explanation:
Understanding Acid-Base Titrations
To determine the number of reactive protons in an unknown acid, one must understand the acid's molecular structure or determine it empirically through experiments, such as a titration with a strong base like NaOH. The mole:mole ratio of acid to base in an acid-base reaction can be found using the balanced chemical equation for the reaction. The stoichiometric coefficients in the balanced equation reflect the proportion of reactants to products and thus indicate this mole:mole ratio.
For example, in the reaction HCl(aq) + NaOH(aq) → NaCl(aq) + H2O, the mole:mole ratio between HCl and NaOH is 1:1. In a titration, the number of moles of a strong base added from a burette to an acid with unknown concentration can be calculated using the concentration of the base and the volume of base added. This information allows one to then determine the number of moles of acid that were present in the solution.
If we have a standard solution of NaOH with a known concentration and we add it to an unknown concentration of HCl until the endpoint of the titration is reached (as signaled by a color change of an indicator or by reaching a certain pH), the number of moles of NaOH used will equal the number of moles of HCl present in the solution because of the 1:1 mole ratio. This information helps in calculating the molarity of the unknown acid solution.