A magnesium$-$lead alloy of mass $6\mathrm{.}5kg$ consists of a solid $$ phase that has a composition just slightly below

the solubility limit at $300C(570F).$ The magnesium$-$lead phase diagram is shown in Animated Figure $9\mathrm{.}20.$

$($a$)$ What mass of lead is in the alloy?

$kg$

$($b$)$ If the alloy is heated to $400C(750F),$ how much more lead may be dissolved in the $$ phase without

exceeding the solubility limit of this phase?

$kg$

Figure $9\mathrm{.}20$