chemistry 12 lab

posted by .

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 -

    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.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry

    We performed a lab in class about a month ago concerning different types of equilibrium. One particular portion of the lab adding 5 mL of .3M HCl to 5 mL of .3 M Pb(NO3)2. After a precipitate finally formed, 8 mL of water was added …
  2. Chemistry

    I did a lab in which I added ionic solutions to tap and distilled water and another ionic solution. Distilled water is the control because it does not react to any solutions since it doesn't contain ions. But one of the lab questions …
  3. Chemistry

    Consider the following reaction: PbCl2 + 2 NaOH -> Pb(OH)2 + 2 NaCl What would be the major species observed floating in solution after one mole of PbCl2 and 2 moles of NaOH are mixed in aqueous solution?
  4. Ions & Atoms-Lab Part 2

    For those who haven't seen my previous post; I request you to go and search for it, it says Lab part 1 on it. You will not know what I'm asking about, if you don't read it it. Overall nothing will make sense. Thank you very much for …
  5. chemistry

    I am completing a lab where I had to determine the mass percent of Mg(OH)2 in an antacid tablet , and I am trying to determine sources of error for my lab. I was wondering if when I back-titrated with NaOH after I overshot on purpose …
  6. Chemistry

    This is for a lab about determining the equilibrium constant. Given: 5.00mL of .203M Fe(NO3)3 mixed with 100mL of .00205M KSCN in a .5M HNO3 solvent for both solutions. Resulting absorbance for solution is .315. How can i find the …
  7. elective mathematics

    A ba contains 5 red and 4 white identical balls abd a second bag contains 3 red and white identical balls If one ball ios selected at random from each of the bags, Find the probability that, two balls selected will be of I)different …
  8. Chemistry

    A solution contains one or more of the following ions: silver, barium, and Copper (II). CY 105 student adds sodium chloride to a small sample of the solution of the unknown and a white precipitate is formed. He/she filters out the …
  9. AP Chemistry

    Consider the following reaction: PbCl2 + 2 NaOH → Pb(OH)2 + 2 NaCl What would be the major species observed floating in solution after one mole of PbCl2 and 2 moles of NaOH are mixed in aqueous solution?
  10. Chemistry

    The indicator HIn has a dissociation constant of 1*10^-4 M. HIn<===> H30^+ + In^- Yellow Red When the pH value of the solution is 7, 1)the indicator shows the colour red 2)at this time most of the indicator has been dissociated …

More Similar Questions