Lab 9

Question 1

What is the crystal violet color in crystal violet due to?

Answer 1

This is the result of the system of alternating single and double bonds, which extends over all three benzene rings.

Question 2

What is conjugation?

Answer 2

This is a system of alternating single and double bonds.

Question 3

What is true of the color of molecules which have conjugation?

Answer 3

The color is very pronounced.

Question 4

What is going on in the following image?

Answer 4

The addition of the hydroxide ion breaks the conjugation of the crystal violet by breaking the central C-C double bond.

Question 5

How do we represent the reaction between crystal violet and OH^-? (NIE)

Answer 5

CV⁺ + OH^- → CVOH

Question 6

What is going to happen to the concentrations of OH^- and CV during the lab?

Answer 6

The concentration of OH^- will more or less stay the same, while the concentration of CV will drop.

Question 7

What is the rate law for the reaction between OH and CV?

Answer 7

rate = k[OH^-]^x[CV⁺]^y

Since [OH^-] is constant under our experimental conditions, this rate law can be written as:

rate = k’[CV⁺]^y where k’ = k[OH^-]^x

Question 8

What is the pseudo rate law? The pseudo rate constant?

Answer 8

This is when you condense a rate law by holding a concentration constant.

This is the constant used in condensing the rate law (k’).

Question 9

What is Beer’s Law? (conceptually)

Answer 9

This is the law that relates absorption of light to the properties of the material being analyzed.