Nitrite (NO2) can be determined by oxidation with excess Ce4+ followed by back titration of the unreacted Ce4+. A 4.030 g sample of solid containing only NaNO2 (FM 68.995) and NaNO3 was dissolved in 500.0 mL. A 25.00 mL sample of this solution was treated with 50.00 mL of 0.1186 M Ce4+ in strong acid for 5 minutes, and the excess Ce4+ was back titrated with 31.13 mL of 0.04289 M ferrous ammonium sulfate, (NH4)2Fe(SO4)2. Calculate the weight percent of NaNO2 in the solid. (78.67%)