2. which of the changes indicated are oxidations
and which are reductions?
a) cu becomes cu2+
b) sn4+ becomes sn2+
c) cr3+ becomes cr6+
d) ag becomes ag+

A) Oxidized

B) Reduced

C) Oxidized

D) Oxidized

Explanation:

A) Cu becomes Cu²⁺

oxidation state increased from 0 to +2. It gets oxidize.

B) Sn⁺⁴ becomes Sn²⁺

oxidation state decreased from +4 to +2. It gets reduced.

C) Cr³⁺ becomes Cr⁺⁶

oxidation state increased from +3 to +6. It gets oxidize.

D) Ag becomes Ag⁺

oxidation state increased from 0 to +1. It gets oxidize.

Oxidation:

Oxidation involve the removal of electrons and oxidation state of atom of an element is increased.

Reduction:

Reduction involve the gain of electron and oxidation number is decreased.

Consider the following reactions.

4KI + 2CuCl₂  →   2CuI  + I₂  + 4KCl

the oxidation state of copper is changed from +2 to +1 so copper get reduced.

CO + H₂O   →  CO₂ + H₂

the oxidation state of carbon is +2 on reactant  side and on product side it becomes  +4 so carbon get oxidized.

practical process described pest part of scientific investigation.

because practical knowledge is powerful then therotical knowledge.