Đáp án đúng: A 5 $\displaystyle \begin{array}{l}\text{C}{{\text{r}}_{\text{2}}}{{\text{O}}_{\text{3}}}\text{+2NaOH}\xrightarrow{{}}\text{2NaCr}{{\text{O}}_{\text{2}}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\\\text{Cr(OH}{{\text{)}}_{\text{3}}}\text{+NaOH}\xrightarrow{{}}\text{NaCr}{{\text{O}}_{\text{2}}}\text{+2}{{\text{H}}_{\text{2}}}\text{O}\\\text{CrO+2HCl}\xrightarrow{{}}\text{CrC}{{\text{l}}_{\text{2}}}\text{+}{{\text{H}}_{\text{2}}}\text{O}\\\text{C}{{\text{r}}_{\text{2}}}{{\text{O}}_{\text{3}}}\text{+6HCl}\xrightarrow{{}}\text{2CrC}{{\text{l}}_{\text{3}}}\text{+3}{{\text{H}}_{\text{2}}}\text{O}\\\text{Cr(OH}{{\text{)}}_{\text{3}}}\text{+3HCl}\xrightarrow{{}}\text{CrC}{{\text{l}}_{\text{3}}}\text{+3}{{\text{H}}_{\text{2}}}\text{O}\end{array}$
