Step 1
The reaction must be written, completed, and balanced:
Li3N(s) + 3H2O(l) → NH3(g) + 3LiOH(aq)
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Step 2
Information provided:
The mass of Li3N = 98.7 g
Information needed:
The molar masses,
Li3N) 34.8 g/mol
H2O) 18.0 g/mol
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Step 3
By stoichiometry,
1 mole Li3N = 34.8 g
1 mole H2O = 18.0 g
Procedure:
Li3N(s) + 3H2O(l) → NH3(g) + 3LiOH(aq)
34.8 g Li3N ---------- 3 x 18.0 g H2O
98.7 g Li3N ----------- X
X = 98.7 g Li3N x 3 x 18.0 g H2O/34.8 g Li3N = 153 g approx.
Answer: 153 g of water