$(25)$ For Equilibrium between $Cr$ and $C{r}_2{O}_3$ at $1100C$

a$)$ Determine the standard enthalpy and entropy of

formation of $C{r}_2{O}_3$ at $298K$ from Ellingham diagram.

b$)$ Read the equilibrium oxygen pressure $p{O}_2(g),p{H}_2\frac{g}{?}$

$p{H}_{2}O(g)$ ratio, and pCO$\frac{g}{p}C{O}_2(g)$ ratio from the

Ellingham diagram using correct scales!

c$)$ Write chemical reactions for $Cr$ used for these three

different scales.

d$)$ What happen above and below these equilibrium values

you read from Ellingham diagram? Use equilibrium constant!!

$(25)$ Why in Ellingham diagrams $G$ vs$.$T data are

a$)$ Linear?

b$)$ Almost parallel between different oxides?