Molten gallium reacts with arsenic to form the semiconductor, gallium arsenide, gaas, used in light emitting diodes and solar cells: ga(l) + as(s) → gaas(s) if 4.00 g of gallium is reacted with 5.50 g of arsenic how many grams of the excess reactant are left at the end of the reaction?

1.2 g

Explanation:

For gallium:-

Mass of gallium= 4.00 g

Molar mass gallium = 69.723 g/mol

The formula for the calculation of moles is shown below:

Thus,

For arsenic:-

Mass of arsenic = 5.50 g

Molar mass of arsenic = 74.9216 g/mol

The formula for the calculation of moles is shown below:

Thus,

According to the given reaction:

1 mole of gallium react with 1 mole of Arsenic

0.0574 mole of gallium react with 0.0574 mole of Arsenic

Moles of arsenic required = 0.0574 moles  

Available moles of arsenic = 0.0734 moles  

Limiting reagent is the one which is present in small amount. Thus, gallium is limiting reagent.

Moles left unreacted of arsenic = 0.0734 moles  - 0.0574 moles  = 0.016 moles

Mass = Moles * Molar mass = 0.016 * 74.9216 g = 1.2 g