Question

In a second atomic absorption experiment, a student prepared a blank solution and measured itsabsorbance, in absorbance units (AU), three times. The measured values were 0.0044 AU, 0.0079 AUand 0.0062 AU.
Required:
a. Calculate the mean of the blank.
b. Calculate the precision of the blank.
c. Calculate the accuracy of the measurement if the true value of the blank is 0.0030 AU.

Answer 1

Answer:

• 0.0062AU
• 0.00082.
• 106.7% error

Explanation:

a.) Average or mean value of readings, $x_{o}$ = (0.0044 + 0.0079 + 0.0062) / 3

= $\frac{0.0185}{3}$ = 0.0062 AU

b.) The accuracy of the readings is determined by taking determining the standard deviation (SD) of the readings:

SD = ∑ $\sqrt{x- x_{o}}$/n

$(0.0062 - 0.0044)^{2}$ = 0.0000032

$(0.0062 - 0.0079)^{2}$ = 0.00000289

$(0.0062 - 0.0062)^{2}$ = 0

SD = $\frac{\sqrt{0.0000032 + 0.00000289 + 0} }{3}$ = 0.00082.

c.) The % accuracy is the distance between the average value and true value

= $\frac{0.0062-0.0030}{0.0030} *100$ = 106.7% error.