At 25oC molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 ohm$$-$$1 cm2 mol$$-$$1 and at infinite dilution its molar conductance is 238 ohm$$-$$1 cm2 mol$$-$$1. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is
A button cell used in watches function as following.
Zn(s) + Ag2O(s) + H2O(l) $$\rightleftharpoons$$ 2Ag(s) + Zn2+(aq) + 2OH$$-$$(aq)
If half cell potentials are
Zn2+(aq) + 2e$$-$$ $$ \to $$ Zn(s); Eo = $$-$$0.76 V
Ag2O(s) + H2O(l) + 2e$$-$$ $$ \to $$ 2Ag(s) + 2OH$$-$$(aq), Eo = 0.34 V
The cell potential will be
A
0.84 V
B
1.34 V
C
1.10 V
D
0.42 V
Explanation
At anode :Zn2+(aq) + 2e$$-$$ $$ \to $$ Zn(s); Eo = $$-$$0.76 V
At cathode : Ag2O(s) + H2O(l) + 2e$$-$$ $$ \to $$ 2Ag(s) + 2OH$$-$$(aq), Eo = 0.34 V
E°cell = E°cathode – E°anode
= 0.34 – (–0.76) = 1.10 V
3
MCQ (Single Correct Answer)
AIPMT 2012 Mains
Molar conductivities $$\left( {\Lambda _m^o} \right)$$ at infinite dilution of NaCl, Hcl and CH3COONa are 126.4, 425.9 and 91.0 S cm2 mol$$-$$1 respectively. $$\left( {\Lambda _m^o} \right)$$ for CH3COOH will be
The Gibb's energy for the decomposition of Al2O3 at 500oC is as follows
$${2 \over 3}$$ Al2O3 $$ \to $$ $${4 \over 3}$$ Al + O2 $$\Delta $$rG = +960 kJ mol$$-$$1 The potential difference needed for the electrolytic reduction of aluminium oxide (Al2O3) at 500oC is at least