Question: The question is incomplete. below is the calibrated data of the question and the answer.
ppm       Absorbance
2130 Â Â Â Â Â 0.048
4260 Â Â Â Â Â 0.110
6400 Â Â Â Â Â 0.173
8530 Â Â Â Â Â Â 0.230
Answer:
% purity = 95.32
Explanation:
NOW MOLAR MASS OF Na2HPO4 =141.96
ATOMIC MASS OF PHOSPOROUS=30.974
141.96/30.974 =4.583 g
If  4.583g of  Na2HPO4 is added in 1000 ml volumetric flask and make the volume to 1L with water, you will get 1000 ppm P solution
Therefore, 2.469g in 100 mL =5387.300 PPM Â
Calculating the percentage error, we have
%ERROR=(5387.300-5146.118)/5146.118 *100
        =4.68
SO %PURITY = 100-4.68 =95.32