Question

Which of the following cation(s) will turn blue in oxidizing flame?
(A) $C{{o}^{2+}}$
(B) $C{{r}^{3+}}$
(C) $N{{i}^{2+}}$
(D) $C{{u}^{2+}}$

Answer 1

Hint: In many types of burners, the flame produced with an excessive amount of oxygen is known as an oxidizing flame.

Complete step by step solution:
-In simple words, the part of a flame that has an excess of oxygen and is capable of oxidizing something that comes in contact is known as an oxidizing flame.

- The flame produced by burners will shorten and its colour will darken when the amount of oxygen increases. An increase in the amount of oxygen also produces hisses and roars.

-When the Bunsen burner is turned on, it produces Bunsen flame to which the air intake can regulate, thereby altering the flow from an intensely hot one- the one in which most of the fuel gases are oxidized to carbon dioxide and water- to a relatively low-temperature flux in which most of the fuel is only partially oxidized. The hotter flame is known as oxidizing flame and the relatively lower flame is known as the reducing flame.

$C{{o}^{2+}}$will turn blue in reducing flame while $C{{u}^{2+}}$will turn blue in an oxidizing flame.

So the correct answers are options A and D.

Note: The part of the flame with low oxygen having yellow or yellowish colour due to carbon or hydrocarbons is known as the reducing flame. The carbon or hydrocarbons present in the flame binds with the oxygen contained in the materials processed with the flame and thereby reduces it. The reducing flame is also known as the Carburizing flame because it tends to introduce carbon into the molten metal.