Lab 1- Determination Of An Equilibrium Constant Flashcards
(14 cards)
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This is true if the product of the reaction is effectively removed from the reaction mixture as a slightly ionized substance, a slightly soluble precipitate or gas, or if a large amount off energy is released by the reaction.
Define Equilibrium
The state where the concentrations of the reactants and the concentrations of the products remain constant in time.
Does equilibrium mean that the chemical reaction has stopped?
No
Do the equilibrium concentrations of reactants and products have to be equal? What happens?
No, they do not; they will constantly be adjusted until the opposing reaction rates are equal.
What color is iodine vapor and what color is HI?
Iodine vapor is violet and HI is colorless.
Is the equilibrium constant always positive?
YES
What does a large value of K (K>1) mean?
It means that the equilibrium favors the formation of products.
What is the equation used for determining the equilibrium constant in this experiment?
Kc= FeSCN2+/(Fe3+)(SCN-)
Since we will be monitoring a chemical reaction in equilibrium, the value of K should _____ regardless of the initial amount of reactants used.
Remain constant
What is the color of the FeSCN2+ solution and what is the maximum absorbance in the spectrophotometer?
Red-447nm
What is the equation for Beer’s Law and what does everything stand for?
A= ebC
A= absorbance; e= molar absorptivity of the species at the measured wavelength (L/mol.cm)
B= path length of the solution in cm
C= concentration of the species in mol/L
In the calibration curve, which of the species has a much higher concentration? What effect does this have?
Fe3+ ; the large excess essentially drives the equilibrium completely to the right, so that you can assume that one mole of FeSCN2+ is produced for each mole of SCN- ion.
How can we calculate the concentration of FeSCN2+?
We use the moles of SCN- since it is the limiting reagent.
What are the steps for determining the value of Kc?
Calculate the Initial Moles of Reactants-Calculate the Moles of Products (to do this, you must combine the volume for each of the reactants and retraen multiply by the given concentration)- Calculate the Moles of Reactants at Equilibrium (Subtract the initial mole value from the mole value of the product)- Calculate the Concentration of the Species (must use the total volume of the solution).
