1
AIEEE 2010
+4
-1
The Gibbs energy for the decomposition of Al2O3 at 500oC is as follows :

$${2 \over 3}A{l_2}{O_3}$$ $$\to$$ $${4 \over 3}Al + {O_2}$$, $${\Delta _r}G$$ = + 966 kJ mol–1

The potential difference needed for electrolytic reduction of Al2O3 at 500oC is at least :
A
4.5 V
B
3.0 V
C
2.5 V
D
5.0 V
2
AIEEE 2009
+4
-1
Given : $$E_{F{e^{3 + }}/Fe}^o$$ = -0.036V; $$E_{F{e^{2 + }}/Fe}^o$$ = -0.439 V
The value of standard electrode potential for the change,
Fe3+ (aq) + e- $$\to$$ Fe2+ (aq) will be
A
-0.072 V
B
0.385 V
C
0.770 V
D
0.270
3
AIEEE 2009
+4
-1
In a fuel cell methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is
CH3OH(l) + 3/2O2 $$\to$$ CO2 (g) + 2H2O (l)
At 298K standard Gibb’s energies of formation for CH3OH(l), H2O(l) and CO2 (g) are -166.2, -237.2 and -394.4 kJ mol−1 respectively. If standard enthalpy of combustion of methanol is -726 kJ mol−1, efficiency of the fuel cell will be
A
87%
B
90%
C
97%
D
80%
4
AIEEE 2008
+4
-1
Given $$E_{C{r^{3 + }}/Cr}^o$$ = -0.72 V; $$E_{Fe^{2+}/Fe}^o$$ = -0.42V, The potential for the cell Cr | Cr3+ (0.1M) || Fe2+ (0.01 M) | Fe is
A
0.26 V
B
0.399 V
C
−0.339 V
D
−0.26 V
EXAM MAP
Medical
NEET