Red Dye Stock Solute Concentration is 0.104M Gatorade red (3mL gatorade 6mL wate
ID: 908357 • Letter: R
Question
Red Dye Stock Solute Concentration is 0.104M
Gatorade red (3mL gatorade 6mL water) (300nm,0.610A)
1) Calculate concentration of each dilute solution made from stock solution (Red Dye)
2) calculate extinction coefficient of each dilute solution.
3) calculate standard dev. of extinction coefficient of Red Dye.
Im having a really hard time with some calculations. And I am not sure that I have been getting the correct answers. Please help
flask Vol. of Dye Vol. of water absorbance A wavelength nm 2x 3mL 3mL 0.878 500 3x 2mL 4mL 0.403 500 5x 1.5mL 6mL 0.657 500 8x 1mL 7mL 0.61 500Explanation / Answer
1) Concentration calculation for dilute solutions,
Using formula,
M1V1 = M2V2
lets say for 2x flask
M1 = 0.104 M
M2 = ?
V1 = vol of dye = 3 ml
V2 = final volume = 3 ml dye +3 ml water = 6 ml
Feed values,
final concentration of diluted dye solution M2 = 0.104 x 3/6 = 0.052 M
Similarly others can be calculated. Data in the table below.
2) Calculating molar extinction coefficient
Now using the formula for absorbance A,
A = ebc
where,
A = absorbance
e = molar extinction coefficient
b = path length = 1 cm
c = concentration
Lets say for flask 2x,
0.878 = e x 1 x 0.052
e = 16.88 M-1.cm-1
Similarly others can be done.
Completed data is given the table
flask Vol dye (ml) Vol water (ml) conc. (M) Absorbance molar extinction coefficient (M-1.cm-1)
2x 3 3 0.052 0.878 16.880
3x 2 4 0.035 0.403 11.510
5x 1.5 6 0.021 0.657 31.286
8x 1 7 0.013 0.610 46.923
3) standard deviation for molar extinction coeffcient,
average = 16.880+11.510+31.286+46.923/4 = 26.65
(26.65-16.88)^2 = 95.4529
(26.65-11.51)^2 = 229.2196
(26.65-31.286)^2 = 21.4925
(26.65-46.923)^2 = 410.9945
mean = 189.28988
standard deviation = sq.rt.(mean) = 13.7583
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