A mixture is known to contain NO−3 and NO−2. Before performing ring test for NO−3, the aqueous solution should be made free of NO−2. This is done by heating aqueous extract with:
A
conc. HNO3
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B
dil. HNO3
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C
urea
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D
zinc dust
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Solution
The correct option is C urea In the mixture of nitrite and nitrate ions, the nitrite ions can be removed by heating with urea and sulphuric acid. 2NaNO2+H2SO4→Na2SO4+2HNO2 2HNO2+CO(NH2)2→CO2+N2+3H2O