Answer:
The correct answer is : d) K₂Cr₂O₇ + KOH ⇒ 2 K₂CrO₄ + H₂O
Explanation:
An oxidation-reduction reaction (redox reaction) is the one in which the number of oxidation of the atoms change, and electrons are shared.
Oxidation: the atom loses electrons and its oxidation number is increased.
Reduction: the atom gains electrons and its oxidation number is decreased.
In the following reactions, the atoms which loses or gains electrons are:
a) 3Br₂ + 2Ga ⇒ 2GaBr₃
Br: its oxidation number changes from 0 to -1 (reduction)
Ga: its oxidation number changes from 0 to +3 (oxidation)
IT IS A REDOX REACTION.
b) H₂S + Cl₂ ⇒ 2HCl + S
Cl: its oxidation number changes from 0 to -1 (reduction)
S: its oxidation number changes from -2 to 0 (oxidation)
IT IS A REDOX REACTION
c) 2PbS + 3O₂ ⇒ 2PbO + 2SO₂
O: its oxidation number changes from 0 to -2 (reduction)
S: its oxidation number changes from -2 to +4 (oxidation)
IT IS A REDOX REACTION
d) K₂Cr₂O₇ + KOH ⇒ 2 K₂CrO₄ + H₂O
There are not changes in oxidation numbers of the atoms:
K : +1
Cr: +6
H: +1
O: -2
IT IS NOT A REDOX REACTION.
