Question

Dissolving potassium chlorate (KClO3) is even more endothermic than potassium chloride.
Your task is to determine how many grams of potassium chlorate you would have to add to 100 mL of water to produce the same temperature change as 5 grams of KCl.

Answer 1

Answer:

The mass of KClO₃ that will absorb the same heat as 5 g of KCl is 3.424 g

Explanation:

Here we have

Heat of solution of KClO₃ = + 41.38 kJ/mol.

Heat of solution of KCl (+17.24 kJ/mol)

Therefore, 1 mole of KCl absorbs +17.24 kJ during dissolution

Molar mass of KCl = 74.5513 g/mol

Molar mass of KClO₃ = 122.55 g/mol

74.5513 g of KCl absorbs +17.24 kJ during dissolution, therefore, 5 g will absorb

$\frac{17.24}{74.5513 } \times 5 \, \, kJ \, or \, 1.156 \, kJ$

Therefore the amount of KClO₃ to be dissolved to absorb 1.156 kJ of energy is given by

122.55 g of KClO₃ absorbs + 41.38 kJ, therefore,

$\frac{1.156}{41.38} \times 122.55 \, g = 3.424 \, g$

Therefore the mass of KClO₃ that will absorb the same heat as 5 g of KCl = 3.424 g.