Answer:
H₂O is the excess reactant
Explanation:
A reactant is in excess when the other reactant is over and the first reactant is still present.
For the reaction:
Mg₂Si (s) 4H₂O (l) → 2Mg(OH)₂(aq) + SiH₄ (g)
We need to convert mass of each reactant to moles in order to find which reactant is in excess as follows:
Moles Mg₂Si -Molar mass: 76.7g/mol-:
50.0g * (1mol / 76.7g) = 0.652 moles of Mg₂Si
Moles H₂O - Molar mass: 18.02g/mol-:
50.0g * (1mol / 18.02g) = 2.78 moles of H₂O
For a complete reaction of 2.78 moles of H₂O are required:
2.78mol H₂O * (1mol Mg₂Si / 4mol H₂O) = 0.694 moles Mg₂Si
As there are just 0.652 moles, Mg₂Si is limiting reactant and
