Filtrate determined by volhard titration

Question

Assignment:

Cobalt 2+ can be analysed by treatment with a known excess of thiocyanate in the presence of pyridine according to the equation: Co₂⁺ + 4C₅H₅N + 2SCN- -------> Co(C₅H₅N)₄(SCN)₂ (s)

The precipitate is filtered off, and the SCN- content of the filtrate is determined by Volhard titration.

Lab Results:

• 25ml of unknown solution was treated with 3ml of pyridine and 25ml of 0.1028M KSCN in a 250ml volumetric flask.
• The solution was diluted to the mark, mixed and filtered.
• After the first few ml's of the filtrate were discarded, 50ml of the filtrate was acidified with HNO₃ and treated with 5ml aliquot of 0.1055M AgNO₃
• After addition of ferroin indicator the excess silver ion required 3.76ml of 0.1028M KSCN to reach the volhard end point.

Provide complete and step by step solution for the question and show calculations and use formulas.