1. How could I show that the nitrate test confirmed that two unknown solutions contained AgNO3
and HNO3, respectively? Please show all Chemical equations that would coorespond to this.
Thank You!!!
Solution
For confirmation of nitrate, follwing test can be done on the two solutions separately
1 st
Test for preliminary confirmation: Copper turnings test
Heating copper turnings along with concentrated sulphuric acid. Brown, pungent effervescence
is observed which turns blue litmus red. Here sulfuric acid reacts with the nitrate ion to form
nitric acid. Nitric acid then reacts with the copper turnings to form nitric oxide. Nitric oxide is
thus oxidised to nitrogen dioxide.
Cu(s) + 4 HNO 3 ? Cu(NO 3 ) 2 + 2 NO 2 +2H 2 O
2 nd
Test for final confirmation: Ring test
The brown ring test can be performed by adding iron(II) sulfate to a solution of a nitrate, then
slowly adding concentrated sulfuric acid such that the acid forms a layer below the aqueous
solution. A brown ring will form at the junction of the two layers, indicating the presence of the
nitrate ion.
The overall reaction is the reduction of the nitrate ion by iron(II) which is oxidised to iron(III)
and formation of a nitrosonium complex where nitric oxide is reduced to NO ?
2HNO 3 + 3H 2 SO 4 + 6FeSO 4 ? 3Fe 2 (SO 4 ) 3 + 2NO + 4H 2 O
[Fe(H 2 O) 6 ]SO 4 + NO ? [Fe(H 2 O) 5 (NO)]SO 4 (brown color) + H 2 O