Cho dãy các chất: \[NaHC{O_3},{\rm{ }}Zn{\left( {OH} \right)_2},{\rm{ }}C{r_2}{O_3},{\rm{ }}Al{\left( {OH} \right)_3},{\rm{ }}Al,{\rm{ }}A{l_2}{O_3},{\rm{ }}AlC{l_3},{\rm{ }}CrO,\]\[Cr{\left( {OH} \right)_3},\]\[Cr{O_3},{\rm{ }}Mg{\left( {OH} \right)_2}.\] Số chất trong dãy có tính chất lưỡng tính là 

Các chất có tính lưỡng tính là: \[NaHC{O_3},{\rm{ }}Zn{\left( {OH} \right)_2},{\rm{ }}C{r_2}{O_3},{\rm{ }}Al{\left( {OH} \right)_3},{\rm{ }}A{l_2}{O_3},{\rm{ }}Cr{\left( {OH} \right)_3}\](6 chất).

* \[NaHC{O_3}\]:

            \[\begin{array}{*{20}{l}}{HCO_3^ - + {\rm{ }}{H^ + } \to {\rm{ }}C{O_2} + {\rm{ }}{H_2}O}\\{\;HCO_3^ - + {\rm{ }}O{H^ - } \to {\rm{ }}CO_3^{2 - } + {\rm{ }}{H_2}O}\end{array}\]

* \[Zn{\left( {OH} \right)_2}\]:

            \[\begin{array}{l}Zn{\left( {OH} \right)_2} + {\rm{ }}2{H^ + } \to {\rm{ }}Z{n^{2 + }} + {\rm{ }}2{H_2}O\;\\Zn{\left( {OH} \right)_2} + {\rm{ }}2O{H^ - } \to {\rm{ }}ZnO_2^{2 - } + {\rm{ }}2{H_2}O\end{array}\]

*\[C{r_2}{O_3}\]:

            \[\begin{array}{*{20}{l}}{C{r_2}{O_3} + {\rm{ }}6{H^ + } \to {\rm{ }}2C{r^{3 + }} + {\rm{ }}3{H_2}O}\\{\;C{r_2}{O_3} + {\rm{ }}2O{H^ - } \to {\rm{ }}2CrO_2^ - + {\rm{ }}{H_2}O}\end{array}\]

*\[{\rm A}l{\left( {OH} \right)_3}\]:

            \[\begin{array}{l}{\rm A}l{\left( {OH} \right)_3} + {\rm{ }}3{H^ + } \to {\rm{ }}A{l^{3 + }} + {\rm{ }}3{H_2}O\\{\rm A}l{\left( {OH} \right)_3} + {\rm{ }}O{H^ - } \to {\rm{ }}AlO_2^ - + {\rm{ }}2{H_2}O\end{array}\]

* \[A{l_2}{O_3}\]:

            \[\begin{array}{*{20}{l}}{A{l_2}{O_3} + {\rm{ }}6{H^ + } \to {\rm{ }}2A{l^{3 + }} + {\rm{ }}3{H_2}O}\\{\;A{l_2}{O_3} + {\rm{ }}2O{H^ - } \to {\rm{ }}2AlO_2^ - + {\rm{ }}{H_2}O}\end{array}\]

*\[Cr{\left( {OH} \right)_3}\]:

            \[\begin{array}{*{20}{l}}{Cr{{\left( {OH} \right)}_3} + {\rm{ }}3{H^ + } \to {\rm{ }}C{r^{3 + }} + {\rm{ }}3{H_2}O}\\{\;Cr{{\left( {OH} \right)}_3} + {\rm{ }}O{H^ - } \to {\rm{ }}CrO_2^ - + {\rm{ }}2{H_2}O}\end{array}\]

Vậy có 6 chất có tính lưỡng tính.

Chọn C.