Using the Richardsen$-$Ellingham diagram, element $(A)=Cu$:$9,Fe$:$8,Si$:$7,Ti$:$6,Mn$:$5,$

Ca:$4,$ Al:$3,$ Ni:$2,$ Mg:$1,$ Co:$0.$ A: second digit before last digit of S$.$Number.

a$)$ Find the equilibrium partial pressure of oxygen in equilibrium in reactions $($i$)$ and $($ii$)$ at below melting point of element A$.$ Take the same temperature all sub questions! Example:TiO$2,u=1,n=2.$ What is the $Kp?$

$($i$)(2\frac{u}{n})A(s)+O_2(g)=(\frac{2}{n})A_{u}On(s)$

$($ii$)\frac{4}{3}Al(s)+O_2($g$)=\frac{2}{3}A{l}_2{O}_3($s$)$

b$)$ Do A and $Cr$ oxidize at $500C$ or below melting point of element $A$ in air? Prove.

c$)$ Let assume that A and $Al$ are mixed to form a $A-Al$ alloy. Solid solution of A and $Al$ contains $x_{Al}=0\mathrm{.}1$ and solute atoms obeys Henrys'law. Henry's activity constant is $6.$ Assume the composition of alloy change during oxidation in air. At equilibrium at alloy$/$oxide interface xAl$=0\mathrm{.}05.$

Express $Kp$ for the Al$.$given in the eq$.$ Below. What is the equilibrium partial presure at this interface?

$\frac{4}{3}Al(s{)}_{(insolution)}+O_2(g)=\frac{2}{3}A{l}_2{O}_3(s)($this reaction happen alloy$/$oxide interface$)$