Current Attempt in Progress

A $1\mathrm{.}5-kg$ specimen of a $88wt\%Pb-12wt\%Sn$ alloy $($Animated Figure $9\mathrm{.}8)$ is heated to $220C$; at this temperature it is entirely an $$ phase solid solution. The alloy is to be melted to the castent that $50\%$ of the specimen is liquid, the remainder being the $$ phase. This may be accomplished either by heating the alloy or changing its composition while holding the temperature constant.

$($a$)$ To what temperature must the specimen be heated?

$($b$)$ How much tin must be added to the $1\mathrm{.}5-kg$ specimen at $220C$ to achieve this state?

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$$ kg