Question

Determine the equation for the best straight line for the calibration curve from the following set of absorbance/concentration (mg/100 mL) data: 0.96/0.0, 0.83/10, 0.66/20, 0.49/30, 0.36/40, 0, 19/50, 0.08/60.

What method did you use to obtain the equation for the best straight line, what is the value of Ao, and what are the numerical value and units of k?

Answer 1

1) According to Beer's Law The slope and intercept of that line provide a relationship between absorbance and concentration:

A = slope c + intercept

The unknown solution is then analyzed. The absorbance of the unknown solution, A_u, is then used with the slope and intercept from the calibration curve to calculate the concentration of the unknown solution, c_u.

cu = (Au - intercept )/ (slope) Hence Cu = (0.2-0.72)/-0.27 = 1.9259 (mg/100 ml) 2) from the provided date let us consider the points for best straight line as below (0, 0.96), (20, 0.66), (40, 0.36) let us consider the equation as y = mx + b Slope = (y2-y1)/(x2-x1) = -0.3/20 = -0.015, let us substitute slope in above equation by considering one point 0.66 = -0.015(20) + b hence slope b = 0.96 4) For 0.59 absorbance unknown concentration cu = (Au - intercept )/ (slope) = (0.59-0.96)/(-0.015 = 24 (mg/100 ml)