Question

Philosopher’s wool on treatment with cobalt nitrate produces:
$(A)CoBa{O_2} \\
(B)CoZn{O_2} \\
(C)CoSr{O_2} \\
(D)CoMg{O_2} \\$

Answer 1

Hint: Zinc oxide is called Philosopher’s wool. ZnO is amphoteric in nature.
Cobalt nitrate has a formula of \[Co{(N{O_3})_2}\] .

Complete answer:
First of all, to approach this question, we need to know what philosopher's wool is. Now we came to know that philosopher’s wool is ZnO, Zinc Oxide.
We also know the formula of cobalt nitrate, as \[Co{(N{O_3})_2}\] .
Now when we mix these 2 substances, the reaction takes place in 2 steps, firstly Cobalt nitrate breaks and the product reacts with zinc oxide.
\[2Co{(N{O_3})_2}\xrightarrow{{\Delta (Heat)}}2CoO + 4N{O_2} + {O_2}\]
Now, the cobalt oxide formed will react with philosopher’s wool ZnO, zinc oxide.
\[CoO + ZnO\xrightarrow{\Delta }CoZn{O_2}\]
This product is Rinnman’s Green.

Thus, the correct option is (B) \[CoZn{O_2}\].

Additional Information: The compound zinc oxide (ZnO) is called philosopher's wool. As a ritualistic ceremonial part, the Alchemists would burn zinc in air and collect the residue, which formed into white woolly tufts.
Alchemist’s started calling this white woolly residue as ‘lana philosophica’ in Latin, which means philosopher's wool in today's life.
Philosopher’s wool is also called white snow, as it is fine, white, non-toxic, powder formed by heating zinc in presence of oxygen.
Philosopher’s wool on treatment with BaO, will give \[BaZn{O_2}\] .

Note: The uses of this white powder, which is Zinc oxide includes:
White pigment in paints.
Component in zinc ointment for treating skin diseases.
Material in sunscreens and sun lotions.
In manufacturing of rubber.
In photocopying products.