Question

consider this reaction:
li₃n (s) + 3h₂o (l) ⟶ nh₃ (g) + 3lioh (l)
you need to make 240 g lioh. how many grams of li₃n (s) must you react with excess water?
350 g
700 g
117 g
1050 g
question 19
1 pts
what does the law of multiple proportions account for?
direction of the arrow in chemical equations
subscripts in chemical formulas
coefficients in chemical equations
coefficients in chemical formulas

Explanation:

Step1: Calculate molar mass

Molar mass of \(LiOH\): \(M_{LiOH}=7 + 16+ 1=24\space g/mol\)
Molar mass of \(Li_3N\): \(M_{Li_3N}=3\times7 + 14=35\space g/mol\)

Step2: Calculate moles of \(LiOH\)

Moles of \(LiOH\), \(n_{LiOH}=\frac{m_{LiOH}}{M_{LiOH}}=\frac{240\space g}{24\space g/mol} = 10\space mol\)

Step3: Use stoichiometry

From the reaction \(Li_3N(s)+3H_2O(l)\to NH_3(g)+3LiOH(l)\), mole ratio \(n_{Li_3N}:n_{LiOH}=1:3\)
So moles of \(Li_3N\), \(n_{Li_3N}=\frac{n_{LiOH}}{3}=\frac{10\space mol}{3}\approx 3.33\space mol\)

Step4: Calculate mass of \(Li_3N\)

Mass of \(Li_3N\), \(m_{Li_3N}=n_{Li_3N}\times M_{Li_3N}=3.33\space mol\times35\space g/mol = 116.55\space g\approx117\space g\)

Answer:

117 g