Al2O3 is reduced by electrolysis at low potentials and high currents. If 4.0 $$ \times $$ 104 amperes of current is passed through molten Al2O3 for 6 hours, what mass of aluminium is product? (Assume 100% current efficiency, at mass of Al = 27 g mol$$-$$1).
The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mho cm2 and at infinite dilution is 400 mho cm2. The dissociation constant of this acid is
Given :
(i) Cu2+ + 2e$$-$$ $$ \to $$ Cu, Eo = 0.337 V
(ii) Cu2+ + e$$-$$ $$ \to $$ Cu+, Eo = 0.153 V
Electrode potential, Eo for the reaction,
Cu+ + e$$-$$ $$ \to $$ Cu, will be
A
0.90 V
B
0.30 V
C
0.38 V
D
0.52 V
Explanation
For the reaction,
Cu2+ + 2e$$-$$ $$ \to $$ Cu, Eo = 0.337 V
$$\Delta $$Go = - nFEo
= – 2 × F × 0.337
= – 0.674 F ......(i)
For the reaction,
Cu2+ + e$$-$$ $$ \to $$ Cu+, Eo = 0.153 V
$$\Delta $$Go = - nFEo
= – 1 × F × – 0.153
= 0.153 F
On adding eqn (i) & (ii)
Cu2+ + e$$-$$ $$ \to $$ Cu+
$$\Delta $$Go = –0.521 F = –nFE°
$$ \Rightarrow $$ E° = 0.52 V
4
AIPMT 2008
MCQ (Single Correct Answer)
Standard free energies of formation (in kJ/mol) at 298 K are $$-$$237.2, $$-$$ 394.4 and $$-$$8.2 for H2O(l), CO2(g) and pentane (g) respectively. The value of Eocell for the pentane-oxygen fuel cell is