Question

Calculate the % of water of crystallization in washing soda crystals.

Answer 1

Hint: The concentration of solution which describes the composition of the solution either qualitatively or quantitatively. To describe the concentration of solution quantitatively more methods are available. There are mass percentages, volume percentage, ppm, mole fraction, normality, molarity, and molality.

Complete step by step solution:
-For expressing the concentration of a component in a particular mixture by mass percentage.
-To calculate the mass percent of the water of crystallization in the given compound washing soda by using the following equation: the formula of mass percentage is expressed as solving for the molar mass for the mass of each element in 1 mole of compound.
-Mass percentage of water of crystallization = $\dfrac{mass\text{ }of\text{ }water\text{ }in\text{ }washing\text{ }soda}{molar\text{ }mass\text{ }of\text{ }washing\text{ }soda}\times 100$
-The molar mass of washing soda = 286.14 g/mol
The molecular formula of washing soda = $N{{a}_{2}}C{{O}_{3}}.10{{H}_{2}}O$
From the chemical formula, washing soda contains 10 molecules of water.
Then, the mass of 10 water molecules in washing soda = 180g
Substitute the above values in the mass percentage of water of crystallization formula, Mass percentage of water of crystallization = $\dfrac{286.14g/mol}{180g}\times 100$= 62.9%

Hence, 62.9% of the water of crystallization in washing soda crystals.

Note: The preparation of washing soda by heating baking soda will give sodium carbonate, carbon dioxide, and water. Washing soda is a white crystalline solid which exists as decahydrate. On heating of washing soda loses its water of crystallization to form monohydrate and continues heating above 373K the monohydrate changes completely to anhydrous white powder called soda ash.