Advertisements
Advertisements
प्रश्न
What is the ‘Ellingham diagram’? Write any ‘two points’ of its significance.
उत्तर
Ellingham diagram:
The graphical representation showing the variation of Gibbs energy with increase of temperature for the formation of oxide (oxidation) is known as Ellingham diagram.
OR
The Ellingham diagram is the plot of free energy change ΔG° against temperature for the reaction of metal and other elements with one mole of gaseous oxygen at 1 atmosphere.
Significance of Ellingham diagram:
- The positive slope of metal oxides shows that their stabilities decrease with increase in temperature. The decrease in their stabilities is due to an increase in ΔG° value.
- The sudden change in the graph shows a phase change, that is, change from solid to liquid or from liquid to vapour.
- The negative slope of CO shows that it becomes more stable with increase in temperature (this is the opposite of that taking place in metal oxides).
- The relative tendency of the metals to undergo oxidation is in the order, as shown below:
Mg > Al > Cr > Fe > Hg > Ag.
This is due to the increase in the negative free energy change of the formation of oxide in the order given below:
MgO > Al2O3 > Cr2O3 > FeO > Ag2O.
APPEARS IN
संबंधित प्रश्न
What is the value of for the following reaction at 298 K -
6CO2+ 6H20(l) → C6H1206(s) + 602(g),
Given that: ΔG° = 2879 kj mol-1, AS = -210 JK-1 mol-1.
With the help of the equation ΔG° = - nFEocell. Explain that cell potential is an intensive property.
Following reactions occur at cathode during the electrolysis of aqueous silver chloride solution :
`Ag^+(aq)+e^(-)rarrAg(s)" "" "" "E^@=+0.80V`
`H^+(aq)+e^(-)rarr1/2H_2(g)" "" "" " E^@=0.00V`
On the basis of their standard reduction electrode potential (E°) values, which reaction is feasible at the cathode and why ?
Calculate ΔrG° for the reaction
Mg (s) + Cu2+ (aq) → Mg2+ (aq) + Cu (s)
Given : E°cell = + 2.71 V, 1 F = 96500 C mol–1
Potential of saturated calomel electrode is-
What is the effect of catalyst on: Gibbs energy (∆G)
What is the effect of catalyst on activation energy of a reaction?
For the reaction
`2AgCl (s) + H_2 (g) ("1 atm") -> 2Ag (s) + 2H^(+) (0.1 M) + 2Cl^(-) (0.1 M)`
`triangleG^0 = -43600 J at 25^@ C`
Calculate the e.m.f. of the cell
`[log 10^(-n) = -n]`
The electrical work done in a galvanic cell is equal to ______
The Gibb's energy change (in J) for the given reaction at [Cu2+] = [Sn2+] = 1 M and 298 K is ______.
\[\ce{Cu(s) + Sn^{2+}(aq) -> Cu^{2+}(aq) + Sn(s)}\]
`["E"_("Sn"^(2+)//"Sn")^0 = -0.16 "V", "E"_("Cu"^(2+)//"Cu")^0 = 0.34 "V", "Take F" = 96500 "C mol"^-1]`
The equilibrium constant at 25°C for the given cell is:
Zn | Zn2+ (1M) | | Ag+ (1M) |
Ag is ______ × 1052.
Given that
\[\ce{E^0_{Zn/Zn^{2+}}}\] = 0.76 V
and \[\ce{E^0_{Ag/Ag^{+}}}\] = −0.80 V
The e.m.f. of cell Zn | ZnSO4 | | CuSO4 | Cu at 25°C is 0.03 V and the temperature coefficient of e.m.f. is −1.4 × 10−4 V/K. The heat of reaction for the change taking place inside the cell is ______ kJ/mol.
The cell potential for the following cell
\[\ce{Pt|H2 (g)| H+ (aq)||Cu^{2+} (0.01 M)| Cu(s)}\]
is 0.576 Vat 298 K. The pH of the solution is ____. (Nearest integer)
The standard Gibbs energy for the given cell reaction in kJ mol-1 at 2'98 K is:
\[\ce{Zn(s) + Cu^{2+} (aq) -> Zn^{2+} (aq) + Cu(s)}\]
E° = 2 V at 298 K
(Faraday's constant, F = 96000 C mol-1)
For a spontaneous reaction, the ΔG, equilibrium constant (K) and `"E"_"cell"^circ` will be respectively.
