Question

A sample of a hydrate of barium chloride weighing $61\, g$ was heated until all the water of hydration is removed. The dried sample weighed $52\, g.$ The formula of the hydrated salt is : (atomic mass, $Ba = 137\, amu. Cl = 35.5\, amu$)

• A. $BaCl _{2} \cdot H _{2} O$
• B. $BaCl _{2} \cdot 2 H _{2} O$
• C. $BaCl _{2} \cdot 3 H _{2} O$
• D. $BaCl _{2} \cdot 4 H _{2} O$

Answer 1

Answer: (B)

$BaCl _{2} \cdot 2 H _{2} O$

Answer 2

$\underset{61 gm}{BaCl _{2} \cdot xH _{2} O} \rightarrow \underset{52}{BaCl _{2}} + \underset{9 gm}{xH _{2} O}$
$52\, gm\, CaCl _{2}$ combines with $9\, gm\, H _{2} O$
$208\, gm BaCl _{2}$ combines with $36\, gm\, H _{2} O$
$n_{H_{2}O}=\frac{36}{18}=2$

So the formula will be, $BaCl _{2} \cdot 2 H _{2} O$