Please show calculations Do the following calculations using a stock standard Al

Question

Please show calculations
Do the following calculations using a stock standard Alphazurine solution of 1.454 x 10–4 M.

1. A 10.00 mL sample of this solution is diluted to 100.0 mL in a volumetric flask.

Determine the concentration of the working standard.

2. Calculate the concentration of a dilution made by mixing 2.00 mL of working standard

with 6.00 ml of distilled water in a large test tube

3. Calculate the absorbance of the dilution prepared in Question #2 if the Spec 20 is set to a

baseline of 98.0 %T and the dilution reads 41.3 %T.

4. A Beer’s Law calibration plot for Alphazurine produced a linear regression equation of

y = 97927x + 0.0198. An unknown solution of Alphazurine is found to have an average%T of 26.9% when the baseline is set to 98.0%T. Calculate the molarity of the unknown

solution.

5. Keep in mind that the slope of the regression equation is equal to “ab” in the Beer’s law

equation of A = abc + intercept. What is the absorptivity, “a” if the pathlength is 1.00

cm?

Explanation / Answer

1. 10ml of stock solution is diluted to 100ml, so 10 time diluted and the final concentration 1.454×10^-4M/10 = 1.454 × 10^-5M

2. 2ml of working std is mixed with 6 ml of distilled water , so dilution is 2ml/8ml = 4 and the concentration is 1.454 × 10^-5M/4 = 3.64 ×10^-6M

3.Absorbance = 2 - log(41.3)

= 0.384

4. y =97927 x + 0.0198

where y = absorbance

x = concentration

Transmittance given as 26.9 and corresponding absorbance is 2- log(26.9) = 0.570

substituting the absorbance value in linear equation we can get concentration

x = (0.570- 0.0198)/97927

= 5.62 × 10^-6MM

5. y = 97927× + 0.0198

Where , ab = 97927

a = molar absorptivity

b = bath length , 1.00cm

Therefore, a = 97927/1.00 = 97927 L/mol cm

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