Question

For ${ CrO }_{ 3 }$, the incorrect statement is:
A.It is called chromic acid
B.It is colorless due to ${ 3d }^{ 10 }$ configuration
C.It is a bright orange solid and color arises due to charge transfer
D.It is toxic and corrosive

Answer 1

Hint: To answer this question you just need to write the electronic configuration of chromium, if you find its d-orbitals are completely filled then it will be colorless. Almost all chemical compounds have some type of adverse effect on living beings.

Complete step by step answer:
-We should know that chromium trioxide (${ CrO }_{ 3 }$) is the acidic anhydride of chromic acid ($H_{ 2 }CrO_{ 4 }$).
-In chromium trioxide, chromium has an oxidation state of +6. This is because oxygen, with an oxidation state of -2, can attach to the atom three times in the chromium oxide compound.
Cr (26) = [Ar] $3d^{ 5 }4s^{ 1 }$
In +6 oxidation state, Cr+6 = [Ar] $3d^{ 0 }4s^{ 0 }$
Hence, its d-orbitals are empty. So, no d-d transitions will occur. Therefore the color of ${ CrO }_{ 3 }$ will be due to charge transfer.
-This is a dark-purple solid under anhydrous conditions.
-It is bright orange when wet and dissolves in water.
-Chromium trioxide is highly toxic, corrosive, and carcinogenic.
-Chromium trioxide, being a powerful oxidizer, will ignite organic materials such as alcohols on contact.
Therefore, we can conclude that the correct answers to this question are options A and B.

Note: We should know that chromium trioxide is mainly used in chrome plating and its other use is on the International Space Station, there it is used to control bacteria growth in the wastewater tank.