Question

When $Mn{O_2}$ is fused with $KOH$ and $KN{O_3}$ a colored compound is formed the product and its color is :
A.${K_2}Mn{O_4},$ Green .
B.$KMn{O_4}$, Purple
C.$M{N_2}{O_3}$, Blue
D.${K_3}Mn{O_2}$, Red

Answer 1

Whenever $Mn{O_2}$ is made to fuse with $KOH$ and $KN{O_3}$ , a purple – green colored compound known as potassium manganate is formed which is known to treat skin infections including the fungal infections.

Complete step by step answer:
$Mn{O_2}$ , this is known as manganese dioxide and is an inorganic compound of blackish or brown color.
$Mn{O_2}$ is a weakly acidic and mildly basic substance and we can somewhat call it an amphoteric substance too.
$KOH$ is potassium hydroxide . It usually becomes tacky in air as it is hygroscopic in nature .
$KN{O_3}$ is called potassium nitrate which is a strong oxidizer used in making fertilizers , medicines etc .
The reaction of $Mn{O_2}$ with $KOH$ and $KN{O_3}$ leads to the production of compound ${K_2}Mn{O_4}$ known as potassium manganate .
The involved reaction is :
$Mn{O_2} + KN{O_3} + KOH\xrightarrow[{KN{O_2}}]{{350 - 450^\circ c}}{K_2}Mn{O_4} + {H_2}O$
${K_2}Mn{O_4}$ is the main product known as potassium manganate that is of green color .
Hence , the option A is the correct one.

Additional information: The manganate salts gets readily disproportionate to permanganate ion and manganese dioxide. The reaction equation can be written as:
${\text{3}}{{\text{K}}_{\text{2}}}{\text{Mn}}{{\text{O}}_{\text{4}}}{\text{ + 2}}{{\text{H}}_{\text{2}}}{\text{O}} \to {\text{2KMn}}{{\text{O}}_{\text{4}}}{\text{ + Mn}}{{\text{O}}_{\text{2}}}{\text{ + 4KOH}}$
-The manganate/manganate (IV) pair is referred to as a chemical chameleon. The reason behind is the colorful nature of disproportionation.
-This green-colored salt is used as an intermediate in the industrial synthesis of potassium permanganate.

Note: The above mentioned reaction in the question should take place in appropriate reaction conditions, that is , it requires a temperature condition of $350^\circ - 450^\circ c$ . Potassium manganate and potassium permanganate should not be mixed up. Both of the compounds have different chemical formulas and even different chemical properties.