Question

An unknown sample of Yellow 6 solution has the absorbance equal to 0.91. The slope of the Beer's law calibration plot constructed using a 3.8E-5M stock solution of Yellow 6 is 0.0117(%)-1. What is the molar ?concentration of the unknown sample (in mole L-1)?Please give your answer to 3 significant figures (1 additional SF is used to minimize rounding errors).

Answer 1

To find the molar concentration of the unknown sample, use Beer's law. Plug in the values for absorbance and molar absorptivity to calculate the concentration.

Step-by-step explanation:

To find the molar concentration of the unknown sample, we can use Beer's law. Beer's law states that absorbance is directly proportional to the concentration of a solution. The equation for Beer's law is A = εcl, where A is the absorbance, ε is the molar absorptivity, c is the concentration, and l is the path length.

In this case, we have the absorbance of the unknown sample (A = 0.91) and the slope of the Beer's law calibration plot (ε = 0.0117(%)-1). We can rearrange the equation to solve for concentration (c): c = A / (ε*l). Plugging in the values, we find: c = 0.91 / (0.0117(%)-1 * 1). Calculating this gives us a concentration of 7.80 x 10-2 M. Rounded to three significant figures, the molar concentration of the unknown sample is 7.80 x 10-2 M.