Question

For chemical disposal, why is dichromate converted to$\mathbf{Cr}\mathbf{\left(}\mathbf{OH}{\mathbf{)}}_{\mathbf{3}}\mathbf{\right(}\mathbf{s}\mathbf{)}$

Short answer

The waste volume is reduced through evaporation.

Step-by-step solution

Defining chemical disposal

Chemical waste is processed based on its physical and chemical qualities. Therefore, waste-product separation is critical. When incompatible materials are mixed in waste streams, unintended reactions can occur, such as the formation of hazardous fumes or explosions, endangering the lives of everyone in the region.

Explaining why dichromate is converted to Cr(OH)3(s) 

$\left(C{r}_2{O}_7^{-2}\right)$dichromate is water-soluble and includes the carcinogen Cr (VI).

For chemical disposal, this dichromate can be transformed to $Cr(OH{)}_{3\left(s\right)}$.

The toxicity of the metal is reduced when $\mathrm{Cr}\left(\mathrm{VI}\right)$is reduced to Cr(III)

As a result, turning aqueous Cr(III) to solid $\mathrm{Cr}(\mathrm{OH}{)}_3$reduces the solubility of the metal and its ability to be distributed by water.

Thus, the waste volume is reduced through evaporation.