Arsenic standard solutions were used to create a calibration curve The current (

Question

Arsenic standard solutions were used to create a calibration curve The current (I) at each arsenic concentration was measured three times. Plot a linear calibration curve by plotting the arsenic concentration on the x-axis (in ppb) and the average of the three current readings at each concentration on the y-axis (in mu A). Use the method of least squares to determine the equation of the line. Using the method of least squares, report the equation of the line: _________________ If the absorbance of an unknown sample is 0.324, what is the concentration? ____________________

Explanation / Answer

Sol:

Take the average of three readings of Abs(1) ,Abs(2),Abs(3) and take the reading for Y axis.

using the least squares the equation is

y=0.022+0.0197(x)

for y=0.324

Find x

substitute in the regression equation obtained.

0.324=0.022+0.0197x

0.324-0.022=0.0197x

0.302=0.0197x

x=0.302/0.0197

x=15.3

Answer 15.3

[As]ppb-x Abs(1) Abs(2) Abs(3) avg(y) 12.4 0.266 0.266 0.268 0.266667 14.3 0.305 0.299 0.308 0.304 16.7 0.355 0.349 0.352 0.352 18.2 0.382 0.383 0.378 0.381 20.7 0.433 0.428 0.43 0.430333 22.4 0.468 0.462 0.46 0.463333

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