A back titration is used when the molar concentration of an excess reactant is known, but the need exists to determine the strength or concentration of an analyte. Back titration is typically applied in acid-base titrations: When the acid or (more commonly) base is an insoluble salt (e.g., calcium carbonate)
Why do we use back titration?
A back titration is useful if the endpoint of the reverse titration is easier to identify than the endpoint of the normal titration, as with precipitation reactions. Back titrations are also useful if the reaction between the analyte and the titrant is very slow, or when the analyte is in a non-soluble solid.
What instances is the back titration utilized?
Back titrations are mainly used in the following cases:
- if the analyte is volatile (e.g., NH3) or an insoluble salt (e.g., Li2CO3)
- if the reaction between analyte A and titrant T is too slow for a practical direct titration.
