$\mathrm{H}_3 \mathrm{PO}_3, \mathrm{H}_2 \mathrm{SO}_4$

$\mathrm{H}_3 \mathrm{PO}_2, \mathrm{H}_2 \mathrm{SO}_3$

$\mathrm{H}_3 \mathrm{PO}_4, \mathrm{H}_3 \mathrm{PO}_2$

$\mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_8, \mathrm{H}_3 \mathrm{PO}_2$

14

12

10

11

CN

$\mathrm{SCN}^{-}$

$\mathrm{SO}_4^{2-}$

$\mathrm{NO}_2^{-}$

urea and formaldehyde

ethylene glycol and phthalic acid

phenol and formaldehyde

1,3-butadiene and styrene