What is the molar concentration of Fe(CN)63- in an aqueous solution that contains 462 mg/L (ppm) of K3Fe(CN)6? Do not use scientific notation in your answer.

Answer 1

First, we look up or calculate the molar mass of K₃Fe(CN)₆. I find it to be 329.25 g/mol = 329.25 mg/mmole.

Next, we calculate how many mmoles of K₃Fe(CN)₆ we have in 462 mg:

463 mg K₃Fe(CN)₆ x 1 mmol/329.25 mg = 1.406 mmoles

Each mmol of K₃Fe(CN)₆ produced 1 mmole of Fe(CN)₆^3- ions, so there are 1.406 mmoles of F₃(CN)₆^3-.

This is in 1 L so molar concentration of F₃(CN)₆^3- = 1.41 mM = 0.00141 M