$3(60)$ Using Ellingham diagram, answer following questions:

a$)$ Read the equilibrium partial pressure of $P{O}_2$ for $Al-A{l}_2{O}_3$ and $Ni-$NiO at $1000C$

b$)$ Determine the standard enthalpy and entropy of change at room temperature for Al$-$

$A{l}_2{O}_3$ reaction.

c$)$ To protect $Al$ and $Ni$ from oxidation what must be the oxygen pressure in the test

atmosphere?

d$)$ Assume you put large amount of $Ni$ and $Si$ in the closed furnace with limited air volume

at $1000C.$ What does happen to $Ni$ and $Al$ after reaction with air? Which element or $s$ and

oxide or s do exist when reactions finish?

Figure $4.$ Standard free energy of formation of some selected oxides $[4].$ The $G^{**}$ cor$-$

responds to the reaction $(2\frac{x}{y})M+O_2=(\frac{2}{y})M,O_{,}.$ The symbols $$ and $.$ identify the melting and boiling points, respectively, of

melting and boiling points, respectively, of the metals: $O$ and $$ identify the melting and

boiling points, respectively, of the oxides.