Question

Which is/are correct among the followings?
Given, the half cell emf's $E_{c{u}^{+2}|Cu}^0=0.337,E_{C{u}^{+1}|Cu}^0=0.521$.

• A. $C{u}^{+1}$ disproportinates.
• B. Cu and Cu${}^{2+}$ comproportionates (reverse of disproportionation into Cu${}^{+}$)
• C. $E_{Cu|C{u}^{+2}}^0+E_{C{u}^{+1}|Cu}^0$ is positive.
• D. All of these

Answer 1

Answer: (A), (C)

The correct options are
A $C{u}^{+1}$ disproportinates.
C $E_{Cu|C{u}^{+2}}^0+E_{C{u}^{+1}|Cu}^0$ is positive.

$Cu\stackrel{reduction}{\leftarrow }C{u}^{+}\stackrel{oxidation}{\to }C{u}^{2+}$
$C{u}^{+1}$ disproportionates because it can oxidize as well as reduce.
$C{u}^{+}\to C{u}^{2+}+Cu$
$E_{cell}^0=E_{C{u}^{+}|C{u}^{+2}}^0+E_{C{u}^{+}|Cu}$
$1e^{-}+C{u}^{+}\to Cu$........................1
$Cu\to C{u}^{2+}+2e^{-}$........................2
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$C{u}^{+}\to C{u}^{+2}+1e^{-}$
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So
$E_{C{u}^{+}|C{u}^{2+}}=1\times 0.521-2\times 0.337=-0.153$
$E_{cell}^0=-0.153+0.521=0.368$ positive, as this is positive so
reaction is spontaneous.
Options A and C are correct.