Molten gallium reacts with arsenic to form the semiconductor, gallium arsenide, GaAsGaAs, used in light emitting diodes and solar cells: Ga(l) + As(s) → GaAs(s)Ga(l) + As(s) → GaAs(s) If 4.00 gg of gallium is reacted with 5.50 gg of arsenic how many grams of the excess reactant are left at the end of the reaction?

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.