JNTU B.Tech I Semester Regular Examinations, November 2008
METALLURGICAL THERMODYNAMICS AND KINETICS
(Metallurgy & Material Technology)
1. (a) What is the absolute thermodynamic temperature scale? Explain why is it called absolute? Discuss.
(b) Write short notes on isothermal and adiabatic process. Give examples.
2. (a) Define and explain the thermal efficiency of a heat engine cycle. Can this be 100%? Discuss.
(b) When entropy change is considered positive or negative as per the usual convention? Explain.
(c) Find the entropy of 1 mole of hydrogen at 1000 0K and 0.1 atm. pressure.
3. (a) Derive Gibb’s-Helmholtz equation and discuss their applicability.
(b) Explain the effect of temperature and pressure on equilibrium constant.
4. (a) Obtain the expression Log P = A
T + B where A & B are constants.
(b) Explain the various forms of the Clausius-Clapeyron equation.
5. Explain the following:
(a) Diffusion along grain boundaries
(b) Diffusion along surfaces.
6. (a) Explain the applications of Ellingham diagrams?
(b) Write the derivation of equilibrium constant?
7. (a) The reversible e.m.f between pure Mg and Mg-Zn alloy containing 63.5 atom
10Mg in a fused KCl-LiCl-MgCl2 electrolyte may be represented by
E = 16.08×10?3 + 1.02×10?5T, where E and T are in V and K respectively. Calculate the activity coefficient and excess partial molar free energy of mixing Mg in the above alloy at 727 0C?
(b) Differentiate between partial molal free energy and standard free energy?
8. (a) Explain why don’t all the collisions be reactant molecules lead to chemical reactions?
(b) The rate constant (k) for the leaching of galena in an aqueous medium containing acetate under oxygen pressure at different temperatures are listed below:
log k -10.9 -11.1 -11.2 -11.5 -12.1 -12.6
1/T×103 2.30 2.35 2.38 2.45 2.61 2.75
Where k and T are expressed in mole2/cm4/min and k respectively, calculate
the activation energy of the leaching process?