Nitrite in a sample is first confirmed by the Griess test (a red azo dye forms). The nitrite is then removed by warming the acidified solution with urea: 2HNO2 + CO(NH2)2 -> 2N2 + CO2 + 3H2O. Using Na 23, N 14, O 16, C 12 and H 1, the minimum mass of urea needed to destroy the nitrite in 0.46 g of NaNO2 is

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Nitrite in a sample is first confirmed by the Griess test (a red azo dye forms). The nitrite is then removed by warming the acidified solution with urea: $2 HNO X_{2} + CO (NH X_{2}) X_{2} 2 N X_{2} + CO X_{2} + 3 H X_{2} O$ . Using Na 23, N 14, O 16, C 12 and H 1, the minimum mass of urea needed to destroy the nitrite in $0.46 g$ of $NaNO X_{2}$ is

M (NaNO X_{2}) = 69

, so nitrite

= 0.46/69 = 0.00667 mol

, giving

0.00667 mol

HNO X_{2}

. The equation (checked for atoms) uses 1 urea per 2

HNO X_{2}

0.00333 mol

. With

M (urea) = 60

, mass

= 0.00333 \times 60 = 0.20 g