Figure $P13$ : Phase diagram for the binary ceramic silica$-$alumina $(Si{O}_2-A{l}_2{O}_3)$ system

A composition of $50$ wt $Si{O}_2-50$ wt$\%A{l}_2{O}_3$ is prepared.

a$.$ At $1700C,$ what phases are present?

b$.$ At $1700C,$ what are the chemical compositions of the phases?

c$.$ At $1700C,$ what are the weight fractions of the phases? Use the

Lever Rule.

d$.$ At $1500C,$ what phases are present?

e$.$ At $1500C,$ what are the chemical compositions of the phases?

f$.$ At $1500C,$ what are the weight fractions of the phases? Use the

Lever Rule

g$.$ What happened when you cooled the composition from $1700C$ to $1500C?$

Why?