Question

Which of the following is the green colored powder and is produced when ammonium dichromate is used in fireworks?
A) $Cr$
B) $Cr{O_3}$
C) $C{r_2}{O_3}$
D) $CrO\left( {{O_2}} \right)$

Answer 1

We must have to know that when ammonium dichromate is used in fireworks, as fireworks involve heating, thus we say that when ammonium dichromate is heated some different colored products are formed. Chromium is a transition metal having atomic number $24$, it belongs to d block element.

Complete answer:
We will look at all the options one by one to solve this question.
Option A) this is an incorrect option as $Cr$ is chromium metal belonging to transition elements, it is silverish grey in appearance and hard in nature thus we can neglect as in the question it is clearly asked for green colored powder.
Option B) this is an incorrect option $Cr{O_3}$ is chromium trioxide and it is dark purple color solid which does not fulfill the question requirement thus this option is not correct.
Option C) this is a correct option as $C{r_2}{O_3}$ is a green colored powder which is formed when ammonium dichromate is used in fireworks. When ammonium dichromate is heated it produces Chromium(III) oxide , dinitrogen gas and water as a product and $C{r_2}{O_3}$ appears to be green in color.
${\left( {N{H_4}} \right)_2}C{r_2}{O_7}\xrightarrow{{Heat}}C{r_2}{O_3} + {N_2} + 4{H_2}O$
Option D) this is an incorrect option as $CrO\left( {{O_2}} \right)$ this is an unstable compound which is known as chromium oxide peroxide thus this option is not right.

Note:
We have to know that the ammonium dichromate has a molecular formula ${\left( {N{H_4}} \right)_2}C{r_2}{O_7}$ when ammonium dichromate is heated it produces a gas with an orange spark which is nitrogen vapor gas and a green solid which is Chromium(III) oxide. Nitrogen gas is being released in this chemical reaction.