nitrite,nitrate and bromide all give brown fumes when added H2so4
how to identify which salt is which?
please explain
nitrite,nitrate and bromide all give brown fumes when added H2so4
how to identify which salt is which?
please explain
The nitrite ion The nitrite ion gives several reactions based on its redox properties.
I3- When it reacts with the I3- anion, the nitrite ion reduces itself to nitric oxide. The student should check the oxidation states of nitrogen in both the cases.
NO2- + 2I3- + 2H+ --> NO(g) + 3I2(aq) + H2O(l)
The yellow color of the I3- ions changes to a greenish tinge which later turns violet. This observation is made in the presence of an oxidizing agent which oxidizes iodine from -⅓ to 0. The O.A. in our case is of course, the nitrite ion.
Before turning violet, a greenish tinge is observed because the increasing concentration of violet color and the decreasing concentration of yellow color during the reaction impart a greenish color.
Lead/Silver Nitrates Most lead and silver compounds show much the same characteristics in analysis. However, lead nitrite is soluble while silver nitrite is an insoluble white solid.
Therefore, to test for the presence of nitrite ions we can use silver and lead nitrate. No precipitate will be observed with lead nitrate, but a white precipitate will form when silver nitrate is added.
2NO2- + Pb2+ -> Pb(NO2)2(aq)
NO2- + Ag+ -> AgNO2(s)
TEST FOR BROMIDES AND IODIDES
Conc. H2SO4 With conc. H2SO4, the florides/chlorides gave HF/HCl respectively. However, the bromides and iodides are oxidized to molecular bromine and iodine respectively!
So, in case of the reaction of iodides/bromides with Conc. H2SO4, bromides give deep brown vapors of Br2, while iodides give violet vapors of iodine.
Silver nitrate solution With silver nitrate solution, bromides give a pale yellow ppt. of AgBr which is partially soluble in NH4OH. Iodides give a yellow ppt of AgI which is insoluble in ammonium hydroxide.
-->Explain this point with reference to Solubility Product and formation constant of the concerned compounds. We need not give a numerical explanation! We just want to emphasize that Inorganic Chemistry is not plain mugging up.
The Chloroform test Take the solution and add an equal amount of chloroform/CHCl3 to it. Add chlorine water and shake vigorously. Watch the change in color of the non-aqueous layer.
If iodide/bromide ions are present, they would be oxidized to Iodine/Bromine respectively. Iodine would impart a violet color to the non-aqueous layer while if bromine is created it will give out a reddish color to the non-aqueous layer.
The same reaction will also occur if dichloromethane is added in replacement of the chloroform.
The nitrite ion gives several reactions based on its redox properties.
I3-When it reacts with the I3- anion, the nitrite ion reduces itself to nitric oxide. The student should check the oxidation states of nitrogen in both the cases.
NO2- + 2I3- + 2H+ --> NO(g) + 3I2(aq) + H2O(l)
The yellow color of the I3- ions changes to a greenish tinge which later turns violet. This observation is made in the presence of an oxidizing agent which oxidizes iodine from -⅓ to 0. The O.A. in our case is of course, the nitrite ion.
Before turning violet, a greenish tinge is observed because the increasing concentration of violet color and the decreasing concentration of yellow color during the reaction impart a greenish color.
Lead/Silver NitratesMost lead and silver compounds show much the same characteristics in analysis. However, lead nitrite is soluble while silver nitrite is an insoluble white solid.
Therefore, to test for the presence of nitrite ions we can use silver and lead nitrate. No precipitate will be observed with lead nitrate, but a white precipitate will form when silver nitrate is added.
2NO2- + Pb2+ -> Pb(NO2)2(aq)
NO2- + Ag+ -> AgNO2(s)
TEST FOR BROMIDES AND IODIDESConc. H2SO4
With conc. H2SO4, the florides/chlorides gave HF/HCl respectively. However, the bromides and iodides are oxidized to molecular bromine and iodine respectively!
So, in case of the reaction of iodides/bromides with Conc. H2SO4, bromides give deep brown vapors of Br2, while iodides give violet vapors of iodine.
Silver nitrate solutionWith silver nitrate solution, bromides give a pale yellow ppt. of AgBr which is partially soluble in NH4OH. Iodides give a yellow ppt of AgI which is insoluble in ammonium hydroxide.
-->Explain this point with reference to Solubility Product and formation constant of the concerned compounds. We need not give a numerical explanation! We just want to emphasize that Inorganic Chemistry is not plain mugging up.
The Chloroform testTake the solution and add an equal amount of chloroform/CHCl3 to it. Add chlorine water and shake vigorously. Watch the change in color of the non-aqueous layer.
If iodide/bromide ions are present, they would be oxidized to Iodine/Bromine respectively. Iodine would impart a violet color to the non-aqueous layer while if bromine is created it will give out a reddish color to the non-aqueous layer.
The same reaction will also occur if dichloromethane is added in replacement of the chloroform.
