Answer:
1.195 g of Arsenic.
Explanation:
Equation of the reaction:
Ga(l) + As(s) → GaAs(s).
Calculating the limiting reagent by:
Number of moles of:
Gallium:
Molar mass of Gallium = 69.7 g/mol.
Mass = 4 g
Number of moles = mass/molar mass
= 4/69.7
= 0.0574 mol.
Arsenic:
Molar mass of Arsenic = 75 g/mol.
Mass = 5.5 g
Number of moles = mass/molar mass
= 5.5/75
= 0.0733 mol
Therefore, using stoichiometry since 1 mole of Gallium reacted with 1 mole of Arsenic. The limiting reagent is Gallium.
Excess reagent is Arsenic.
Number of moles excess = 0.0733 - 0.0574
= 0.0159 moles
Mass of the excess Arsenic left =
Molar Mass * number of moles
= 0.0159 * 75
= 1.195 g of Arsenic.