Chapter 10, Problem 181A

Table 4 shows data from an experiment to determine the formulas of hydrated barium chloride. Determine the formula for the hydrate and its name.

Interpretation Introduction

Interpretation:

The formula and name of the given hydrate of barium needs to be determined.

Concept introduction:

Number of water molecules present per molecule of a compound is known as water of crystallization.

Answer to Problem 181A

Name of the hydrate is barium chloride dihydrate.

Formula is BaCl₂.2H₂O.

Explanation of Solution

Molar mass of BaCl₂ is 208 g/mol.

Molar mass of H₂O is 18 g/mol.

Total mass of hydrated salt and crucible is 31.35 g.

Mass of the crucible is 21.30 g

Thus,

Mass of hydrated salt $\text{=(31}\text{.35-21}\text{.30) g =10}\text{.05 g}\text{.}$

Mass of the salt and crucible after 5 minutes heating is 29.87 g.

Mass of anhydrous salt $\text{=(29}\text{.87-21}\text{.30) g =8}\text{.57 g}\text{.}$

Now, number of moles of barium chloride and water can be calculated as follows:

$n=\frac{m}{M}$

Thus,

Moles of BaCl₂$=\frac{8.57\text{ g}}{208\text{ g/mol}}=0.04\text{1 mol}$

Moles of H₂O $=\frac{1.48\text{ g}}{18\text{ g/mol}}=0.082\text{ mol}$

Moles ratio of BaCl₂:H₂O $=0.041:0.082=1:2.$

Formula is BaCl₂.2H₂O.

Conclusion

Thus, the formula of the hydrate is BaCl₂.2H₂O which is called barium chloride dihydrate.