Question

During the experiment the cuvettes are kept in a water bath between absorbance readings. What is the main purpose these are kept in a water bath?

A)The water bath is used to keep the cuvettes clean to ensure that they obtain a consistent absorbance reading

B) The water bath is used to dilute the solutions

C)The water reacts with the reactants in the cuvette to form a colored solution

D) The water bath is used to maintain a constant temperature for the solutions and should be checked periodically

When looking at the plots, from your data, for the first and second order graphs, what observations will let help you determine the order of your graph?

	The proper order graph will fit an exponential curve
	The proper order graph will have R2 values closer to 1 with a linear fit
	The proper order graph will have R2 values closer to 1 with a quadratic fit
	If both graphs look exactly the same the order can be determined
	The proper order graph will fit a straight line In order to calculate the amount of product formed later in the experiment, the initial concentration of the Cr3+reactant in solution must be determined. Calculate the molarity of Cr3+ when 5.51 mL of 0.0200M Cr(NO3)3 is diluted with 20.00mL of Na2H2EDTA (assuming only dilution).

Answer 1

1) : During experiments, cuvettes are kept in water bath to maintain a constant temperature. Because fluctuation in temperature may cause variation in the observed absorbance. Molecular vibrations are dependent on surrounding temprature and hence its absorption spectra as well also be affected by surrounding temprature. So the answer is option D.

2) : The proper order graph will fit an exponential curve with equation : y = ab^x ...where b<1.

3) M1V1 = M2V2

Where, M1 = 0.02 M, V1 = 5.51 mL and V2 = 20 mL

Thus, M2 = (M1V1)/ V2 = (0.02 5.51) / 20 = 0.00551 M

Concentration of Cr3+ after dilution = 0.00551 M.