Question

The acid used in the detection of phosphorus in an organic compound is:

• A. $H_{2}S{O}_4$
• B. $HN{O}_3$
• C. $HCl$
• D. any of the above

Answer 1

The correct option is B $HN{O}_3$

To check the phosphorous conent in organic compound ,the given organic compound is treated with sodium peroxide($N{a}_2{O}_2$). Phosphorus gets converted to sodium phosphate.

The aqueous mixture is heated with concentrated nitric acid and ammonium molybdate. A yellow precipitate of ammonium phosphomolybdate is produced. This yellow precipitate helps us conclude that Phosphorus was present in the organic compound

$Na_3PO_4+3HNO_3\rightarrow H_3PO_4+3NaNO_3$

$H_3PO_4+12(NH_4)_2MoO_4+21HNO_3\rightarrow (NH_4)_3PO_4⋅12MoO_3 (yellow ppt⋅)+21NH_4NO_3+12N_2O$

Hence option B is correct.