(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Chem lab on equilibrium. We added the same amount of Fe(NO3)2 (5ml) to varying amounts of KSCN and used a given Beer's law and absorption data to calculate concentration of FeSCN2+ and then calculate the Eq. constant (K).

I calculated the Eq. constant, but I'm stuck on two follow up questions:

Consider the equation Fe+3(aq) + SCN(-)(aq) <---> FeSCN 2+

Which ion (Fe3+) or SCN (-) is never in excess? Why?

What experimental conditions are needed to ensure "all" SCN(-) is present as FeSCN2+

2. Relevant equations

The intro we were given in our lab manual described the instability of Fe2+ in water (how it forms Fe3+). Also described the colors of Fe and FeSCN2+. Also defined complex ions and oxidation states.

3. The attempt at a solution

I don't understand how I would know which ion is limiting. We used varying amounts of KSCN and kept the amount of FeNO3 consistent. The stoichiometry would indicate it's a 1:1 ratio. According to the calculations I did for one trial, I end up with fewer moles of SCN(-) at equilibrium, so does that mean it's limiting?

Any guidance on how to figure this out would be appreciated.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Equilibrium chem lab (FeSCN2+)

Can you offer guidance or do you also need help?

Draft saved
Draft deleted

**Physics Forums | Science Articles, Homework Help, Discussion**