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

The reaction equation is:

Ba (OH) ₂ * 8H ₂ O + 2NH ₄ SCN (s) → Ba (SCN) ₂ (s) + 10H ₂ O (l) + 2NH ₃ (g)

The molecular mass of barium hydroxide octahydrate is 315 grams / mol.

We determine the number of moles of barium hydroxide octahydrate:

moles = mass / Mr

moles = 6.5 / 315

moles = 0.02 mol

Using the equation, we can determine that the moles of ammonium thiocyanate required are:

2 * 0.02 = 0.04 mol

The molecular weight of ammonium thiocyanate is 76.1 grams / mol

Weight = moles * Mr

Weight = 0.04 * 76.1

Weight = 3.04 grams

3.04 grams of ammonium thicyanate are required.