Kemija - 2012./13. ljeto - 26.

${\mathrm{N}\mathrm{O}}_2{}^{-}\backslash mathrm\{NO\}\_\{2\}\{\; \}^\{-\}$

${\mathrm{H}}_2\mathrm{O}\backslash mathrm\{H\}\_\{2\}\; \backslash mathrm\{O\}$

${\mathrm{H}\mathrm{N}\mathrm{O}}_2\backslash mathrm\{HNO\}\_\{2\}$

${\mathrm{O}\mathrm{H}}^{-}\backslash mathrm\{OH\}^\{-\}$