Question

Which of the following processes does not involve either oxidation or reduction?

• A. Heating Mercuric Oxide
• B. Formation of slaked lime from quick lime
• C. All of the above
• D. Formation of Manganese Chloride from Manganese oxide

Answer 1

The correct option is B Formation of slaked lime from quick lime

Here, in this reaction $CaO+H_{2}O\to Ca(OH{)}_2$, Oxidation number doesn’t change so its not a redox reaction.

(b):
$\underset{\text{Mercuric oxide (red)}}{2HgO\left(s\right)}\underset{decomposition}{\overset{Thermal}{\to }}\underset{\text{Mercury silver liquid}}{2Hg\left(l\right)}+O_2\left(g\right)\uparrow$

In the above reaction the Hg is reduced from "+2" to "0" & oxygen is oxidised from "-2" to "0".

(c):
$\underset{\text{Manganese dioxide}}{Mn{O}_2\left(s\right)}+4HCl\left(aq\right)\to \underset{\text{Manganese chloride}}{MnC{l}_2\left(aq\right)}+2H_{2}O\left(l\right)+C{l}_2\left(g\right)$

In this reaction Mn is reduced from "+4" to "+2" & Cl is oxidised from "-1" to "0".
Hence options (b) & (c) both contain redox reactions.