Mass As₂I₄ actually isolated : 626.27 g
Reaction
2As+4AsI₃⇒3As₂I₄
mass As : ρ x V
[tex]\tt 5.72\times 3^3=5.72\times 27=154.44~g[/tex]
mol As (MW 75 g/mol) :
[tex]\tt \dfrac{154.44}{75}=2.059[/tex]
mol AsI₃ :
[tex]\tt \dfrac{1.01\times 10^{24}}{6.02\times 10^{23}}=1.68[/tex]
Limiting reactant :
As:AsI₃ =
[tex]\tt \dfrac{2.059}{2}:\dfrac{1.68}{4}=1.03:0.42(AsI_3~smaller\rightarrow limiting~reactant)[/tex]
mol As₂I₄ :
[tex]\tt \dfrac{3}{4}\times 1.68=1.26[/tex]
mass As₂I₄ (Mw=657.461 g/mol)
[tex]\tt 1.26\times 657.461=828.4~g[/tex]
For 75.6% yield :
[tex]\tt 0.756\times 828.4=626.27~g[/tex]