Answer to Question #188832 in Chemistry for Christine

Question

What mass of ammonium thiocyanate must be used if it is to react completely with 6.5g barium hydroxide octahydrate?

Answer 1

Ammonium thiocyanate = NH₄SCN

Barium hydroxide octahydrate = Ba(OH)₂ · 8H₂O

Solution:

Balanced chemical equation:

2NH₄SCN + Ba(OH)₂ · 8H₂O → Ba(SCN)₂ + 2NH₃ + 10H₂O

According to the equation above: n[NH₄SCN]/2 = n[Ba(OH)₂ · 8H₂O]

The molar mass of Ba(OH)₂ · 8H₂O is 315.46 g/mol.

Hence,

n[Ba(OH)₂ · 8H₂O] = (6.5 g) × (1 mol / 315.46 g) = 0.020605 mol

n[NH₄SCN] = 2 × n[Ba(OH)₂ · 8H₂O] = 2 × 0.020605 mol = 0.04121 mol

The molar mass of NH₄SCN is 76.122 g/mol.

Hence, the mass of NH₄SCN will be:

m(NH₄SCN) = (0.04121 mol NH₄SCN) × (76.122 g NH₄SCN / 1 mol NH₄SCN) = 3.137 g NH₄SCN

Mass of NH₄SCN = 3.137 g = 3.14 g

Answer: 3.14 grams of ammonium thiocyanate (NH₄SCN) must be used.