Trước phản ứng: \(\left[ {{{\rm{H}}_2}} \right] = \left[ {{{\rm{I}}_2}} \right] = \frac{{0,04}}{2} = 0,02({\rm{M}})\)

                 H2(g)+I2( g)⇌2HI(g)

\({{\rm{K}}_{\rm{c}}} = \frac{{{{[{\rm{HI}}]}^2}}}{{\left[ {{{\rm{H}}_2}} \right]\left[ {{{\rm{I}}_2}} \right]}} = \frac{{{{(2{\rm{x}})}^2}}}{{(0,02 - {\rm{x}})(0,02 - {\rm{x}})}} = 64\)

\( \Rightarrow {\rm{x}} = 0,016{\rm{M}} \Rightarrow [{\rm{HI}}] = 2{\rm{x}} = 0,032\)M. Làm tròn: \([{\rm{HI}}] = 0,03{\rm{M}}\)