lab 13 spectrophotometric determination of an EQ constant Flashcards
what are the safety considerations for nitric acid 0.1 M
- can cause mild skin irritation
- can cause moderate eye damage
- you must wear goggles at all times
what are the safety considerations for sodium thiocyanate solution?
- can cause serious eye damage
- acute toxicity from ingestion
- you must wear goggles at all times
what is the objective of this lab
determine the equilibrium constant of a chemical reaction using absorption spectroscopy of Beer’s law
review the sceenshot, pay attention to the notes
what do you need to know in order to calculate the Kc value of the reaction (the c after the K is snall)
need to know the concentrations of each of the species at equilibrium
what is Kc (tiny c)
generic notation for equilibrium constant
what is Kt (tiny t)
notation for equilibrium constant when a coordination complex is be formed
how do you determine the Kc value of the iron(III)/thiocyanate reaction (the c after the K is tiny)
A. Prepare solutions of known [FeSCN2+]eq {standards}
B. Measure the absorbance of each of the solutions of known concentration
C. Prepare a Beer’s law plot of Absorbance vs [FeSCN2+]eq for the solutions of known concentration
D. Prepare solutions of various unknown [FeSCN2+]eq
E. Measure the absorbance of each of the solutions of unknown concentration
F. Use the Beer’s law plot to determine the [FeSCN2+]eq in the unknown solutions
G. Use the [FeSCN2+]eq in the unknown solutions to determine the [Fe3+]eq and [SCN-]eq
look at the screenshot to see how the things in [ ] really should look
what is this?
pipet man / wheel / cheater
what are these?
10-mL Mohr (graduated) pipets
what do you need to do to prepare solutions of known [FeSCN^2+]
obtain
- 6 clean dry 6-inch test tubes
- test tube rack
- three 10-mL Mohr (graduated) pipets
- pipet man / wheel / cheater
- two clean dry 50-mL beakers
- one clean dry 150-mL beaker
- one 400 or 600-mL beaker for waste
after gathering
