0.100 g of a sample containing sodium nitrite (molar mass 69) is treated with 25.0 mL of 0.0200 M $\mathrm{KMnO}{}_4$ in acid (excess), $\mathrm{NO}{}_2{}^{-}$ going to $\mathrm{NO}{}_3{}^{-}$. The unreacted permanganate is then back-titrated with 0.0500 M oxalic acid, needing 20.0 mL. Which of the following are correct?

1. AThe permanganate added is equivalent to 2.50 meq
2. BThe unreacted permanganate is 0.200 mmol
3. CThe sample contains 0.250 mmol of $\mathrm{NaNO}{}_2$
4. DThe sample is 34.5% $\mathrm{NaNO}{}_2$