A Beer\'s Law graph obtained by plotting absorbance versus concentration in mol/

Question

A Beer's Law graph obtained by plotting absorbance versus concentration in mol/L for a series of standard solutions, produced a straight line with equation y = 2700.1 x Suppose an unknown SCN solution is treated in exactly the same manner as described in Part B of the procedure. The final diluted solution gives an absorbance reading of 0.265.

Part B Procedue: 10mL of unknown into a 100mL flask and dilute solution with 0.1M HNO3. Pipet 10mL of diluted solution into a 25mL flask. Add 10mL of 0.15M Fe solution and dilute yo mark with 0.1HNO3.

1. Determine the [FeSCN2+] in this diluted solution. Answer = 9.81×10-5 M

2. Determine the SCN concentration in the original (undiluted) unknown solution.

Explanation / Answer

Beers law:

A = e*l*M

where "e*l" in this case is the slope, x = M and y = A

so

A = 2700.1*M

substitute for A= 0.265

M = A/2700.1 = 0.265/

0.265/2700.1 = 0.00009814451 = 9.81*10^-5 M

for Q2. Add Part 1, since it is required for initial conditions of SCN- and Fe+3 ions

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