Solubility & T



Effect of Temperature on Solubility

As the temperature of a liquid increases, the solubilities of gases in that liquid decrease. We can use the Second Law of Thermodynamics to explain why. Heating a solution of a gas enables the particles of gas to move more freely between the solution and the gas phase. The Second Law predicts that they will shift to the more disordered, more highly dispersed, and therefore, more probably gas state.

In a similar way, we can explain why the substances that are solids at room temperature and pressure tend to become more soluble when the temperature rises. Heating a solution of a solid makes it easier for the particles of solid to move between the solution and the solid phase. The Second Law predicts that they will shift to the more disordered, more highly dispersed, and therefore, more probably solution state.

The table below shows the relationship between temperature and solubility for several substances. Notice that substances that are gases at room temperature and pressure become less soluble with increased temperature, and the substances that are solids at room temperature and pressure tend to become more soluble when the temperature rises.

Temperature and Water Solubilities in Grams of Solute per 100 mL of Water

Temperature   C

Solid citric acid Solid potassium phosphate Gaseous nitrogen Gaseous oxygen
0 49 44 0.0030 0.0070
20 59 50 0.0020 0.0050
30 64 * * *
50 71 62 * 0.0031
70 76 * * *
100 84 * * 0.0029

*Not available

Click here to see an example. 

Click here to see an exercise. 

  bishopmark@comcast.net

Home ] Up ] Example ] Exercise ]