30.0 g of KCl are dissolved in 100.0 ml of water at 45 degrees C. How many additional grams of KCl are needed to make the solution saturated at 80 degrees C?

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Potassium chloride (KCl) is soluble in water. Like all other solutes, its solubility in water is also a function of temperature. As the temperature of the solvent goes up, so does the solubility of the salt. One can experience this very easily with sugar. 

The solubility of KCl at 45...

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Potassium chloride (KCl) is soluble in water. Like all other solutes, its solubility in water is also a function of temperature. As the temperature of the solvent goes up, so does the solubility of the salt. One can experience this very easily with sugar. 

The solubility of KCl at 45 degrees C is 41.49 g per 100 g of water. Since the density of water can be approximated to about 1 g/ml (it is 0.97 g/ml at 80 degrees C), we can say that 41.49 g of KCl can be dissolved in water at 45 degrees C. 

Since, we have added only 30 g of KCl, the solution is not yet saturated with KCl.

At 80 degrees C, the solubility of KCl is 51.19 g per 100 g of water (or 100 ml of water). Since, there is only 30 g of KCl in the water, we need 21.19 g (= 51.19 - 30) more KCl for saturation at 80 degrees C.

 

Hope this helps. 

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