Question

(d) Justify that the following reaction is a Redox reaction. Identify the species oxidized reduced, which
acts as an oxidant and which acts as a reductant.
[2]
1 (aq) + 25,0, (aq) → 5,0" (aq) + 21°(aq)

Answer 1

$Answer$

$\bf (a) CuO_{(s)}+ H_{2(g)}→ Cu_{(s)}+ H_2O_{(g)}$

Let us write the oxidation number of each element involved in the given reaction as:

$\bf \qquad+2  -2    \bf \qquad     0     \bf \qquad         0            \bf \qquad  +1    -2$

$\bf \: CuO_{(s)}+ H_{2(g)}→ Cu_{(s)}+ H_2O_{(g)}$

Here, the oxidation number of Cu decreases from +2 in CuO to 0 in Cu i.e., CuO is reduced to Cu. Also, the oxidation number of H increases from 0 in$H_2$to +1 in$H_2$Oi.e., $H_2$

is oxidized to$H_2$ O.

Hence, this reaction is a redox reaction.

$\bf(b) Fe_2O_{3(s)}+ 3CO_{(g) }→ 2Fe_{(s)} + 3CO_{2(g)}$

Let us write the oxidation number of each element involved in the given reaction as:

$\bf \: \qquad+3   -2    \bf \qquad       +2  -2       \bf  \qquad     0         \bf \qquad  +4  -2$

$\bf \: Fe_2O_{3(s)}+ 3CO_{(g) }→ 2Fe_{(s)} + 3CO_{2(g)}$

Here, the oxidation number of Fe decreases from +3 in $Fe_2O_3$to 0 in Fe i.e., $Fe_2O_3$is reduced to Fe.

On the other hand, the oxidation number of C increases from +2 in CO to +4 in $CO_2$i.e., CO is oxidized to$CO_2$. Hence, the given reaction is a redox reaction.

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