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प्रश्न
The reaction,
Cr2O3 + 2Al → Al2O3 + 2Cr
(ΔGθ = -421kJ) is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?
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उत्तर १
The change in Gibbs energy is related to the equilibrium constant, K as
`triangleG = -RTInK`
At room temperature, all reactants and products of the given reaction are in the solid state. As a result, equilibrium does not exist between the reactants and the products. Hence, the reaction does not take place at room temperature. However, at a higher temperature, chromium melts and the reaction takes place.
We also know that according to the equation
`triangleG = triangleH-TtriangleS`
Increasing the temperature increases the value of `TtriangleS` making the value of `triangleG` more and more negative. Therefore, the reaction becomes more and more feasible as the temperature is increased.
उत्तर २
This is explained on the basis of Keq, the equilibrium constant. In the given redox reaction, all reactants and products are solids at room temperature, so, there is no equilibrium between the reactants and products and hence the reactions does not occur at RT. At high temperature, Cr melts and values of TAS increases. As a result, the value of `triangle_rG^theta` becomes more negative and hence the reaction proceeds rapidlyt
संबंधित प्रश्न
How is ‘cast iron’ different from ‘pig iron’?
Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.
State the role of silica in the metallurgy of copper.
Write chemical reactions taking place in the extraction of copper from Cu2 S.
How will you convert the following:
Zinc blende to Zinc metal
Choose the correct option of temperature at which carbon reduces \[\ce{FeO}\] to iron and produces \[\ce{CO}\].
For the reduction of \[\ce{FeO}\] at the temperature corresponding to point D, which of the following statements is correct?
For the metallurgical process of which of the ores calcined ore can be reduced by carbon?
(i) Haematite
(ii) Calamine
(iii) Iron pyrites
(iv) Sphalerite
Wrought iron is the purest form of iron. Write a reaction used for the preparation of wrought iron from cast iron. How can the impurities of sulphur, silicon and phosphorus be removed from cast iron?
The purest form of iron is prepared by oxidising impurities from cast iron in a reverberatory furnace. Which iron ore is used to line the furnace? Explain by giving reaction.
The mixture of compounds A and B is passed through a column of \[\ce{Al2O3}\] by using alcohol as eluant. Compound A is eluted in preference to compound B. Which of the compounds A or B, is more readily adsorbed on the column?
Why is sulphide ore of copper heated in a furnace after mixing with silica?
Explain the following:
\[\ce{CO2}\] is a better reducing agent below 710 K whereas \[\ce{CO}\] is a better reducing agent above 710 K.
Explain the following:
Silica is added to the sulphide ore of copper in the reverberatory furnace.
A cuprous ore among the following is:-
Carbon deposition reaction taking place in ______.
\[\ce{Au + CN^- + H2O + O2 -> [Au(CN)2]^- + OH^-}\]
The number of CN− ions involved in the balanced equation is ______.
