A student has prepared an experiment to determine the concentration of X (aq) in an unknown sample. The absorbance at different concentrations is shown below:
Calibration curve built using standard samples of X
If the absorbance of the unknown sample is 0.275 at 420 nm, what is the concentration of X in the unknown sample?
Answer:
Step 1: Set up the equation of the line to show the relation between absorbance and concentration
Step 2: Calculate the gradient (m) for the equation of the line of the calibration curve, using the data for two nearest standard solutions
m = 60
Step 3: Calculate the y axis intercept (b) for the calibration curve by replacing A and c with one of the data points used in Step 1
Step 4: Complete the equation of the line for the calibration curve using the calculated values of m and b
Step 5: Rearrange the equation of the line in terms of the concentration (c)
Step 4: Calculate the concentration of X in the unknown sample, using the absorbance given in the problem statement by replacing its value in the equation obtained in st