Question

A student is using a program to analyze the ditigal image of a colorimetric assay. The student measures pixel intensity (gray value) of a blank sample with 217 and of a standard sample with 140. What is the absorbance equivalent value of the standard sample? State your answer using 3 significant figures

Answer 1

Solution:

Here, we are going to calculate the  absorbance equivalent value of the standard sample.

Step 1:

Black sample =217 (three significant figures)

Standard sample =140 =14 x 101 (two significant figures)

The absorbance equivalent value of the standard sample =(217-140) =77

=77.0

As we know, Zeros at the end of a number are significant if it contains a decimal point.

Therefore, the  absorbance equivalent value of the standard sample 3 significant figures is 77.0