To determine the purity of a sample of Na2HPO4, a 2.469-g sample is dissolved and diluted to volume in a 100-mL volumetric flask. Analysis of the resulting solution gives an absorbance of 0.135. What is the purity of the Na2HPO4

Question: The question is incomplete. below is the calibrated data of the question and the answer.

ppm             Absorbance

2130           0.048

4260           0.110

6400           0.173

8530            0.230

% 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  

Calculating the percentage error, we have

%ERROR=(5387.300-5146.118)/5146.118 *100

               =4.68

SO %PURITY = 100-4.68 =95.32