Homework Help: chemistry 12 lab

Posted by cel on Friday, November 5, 2010 at 11:47pm.

We did a lab on equilibrium and this is one of the following questions:

When Ag ions are added to FeSCN ions (which are red in colour), the colour disappears, and a white precipitate of AgSCN forms.

The question is.. Explain why Fe can be used as an indicator in a reaction to determine the concentration of an unknown solution of Ag by reaction it with a solution of KSCN of known concentration.

chemistry 12 lab - DrBob222, Saturday, November 6, 2010 at 12:25am
I don't see this as a problem. The whole idea is that Ag ion reacts and ppts with SCN ion to form AgSCN (due to the extreme insolubility of AgSCN Ksp = 1+ x 10^-12). The next drop of SCN ion, after all of the Ag ion has reacted, is free to form the complex with Fe(III) of FeSCN^+2. You have no FeSCN^+2 ions at the beginning of the titration, only at the end of the titration. Until the end point is reached, Ksp is so small for AgSCN that FeSCN^+2 doesn't form until all of the Ag ion is gone.

Answer this Question

Related Questions

chemistry - I am completing a lab where I had to determine the mass percent of ...
Chemistry - I did a lab in which I added ionic solutions to tap and distilled ...
Chemistry - I had an equilibrium laboratory and had to answer a few questions ...
Chemistry - Consider the following reaction: PbCl2 + 2 NaOH -> Pb(OH)2 + ...
Chemistry - This is for a lab about determining the equilibrium constant. Given...
chemistry - Write the formula of the ionic compound that forms between a. copper...
chemistry - Lab: Creating a Redox Table Purpose: The purpose of this lab ...
10th grade chemistry - We're doing a lab report on the hardness of water, ...
Chemistry Titration Lab - okay, so i have NO idea how to figure out the ratio of...
chemistry lab - Explain how the differences in the solubility products of AgI ...

For Further Reading

First Name:
School Subject:
Answer: