Effects of Temperature and Pressure on Solubility - Chemistry LibreTexts
Effect of Temperature and Pressure on the Solubility of Carbon Dioxide in .  examined the relationship between pressure, and the salinity of the water and. Solubility - Understand the meaning of Solubility, solute, solvent, saturated & unsaturated solution. Factors affecting solubility of solution, Henry's Law. To understand the relationship among temperature, pressure, and solubility. Experimentally it is found that the solubility of most compounds depends strongly on.
Let's start with temperature: For Gases, solubility decreases as temperature increases duh The physical reason for this is that when most gases dissolve in solution, the process is exothermic. This means that heat is released as the gas dissolves.
This is very similar to the reason that vapor pressure increases with temperature. Increased temperature causes an increase in kinetic energy. The higher kinetic energy causes more motion in the gas molecules which break intermolecular bonds and escape from solution. Check out the graph below: As the temperature increases, the solubility of a gas decreases as shown by the downward trend in the graph. For solid or liquid solutes: Decrease in solubility with temperature: If the heat given off in the dissolving process is greater than the heat required to break apart the solid, the net dissolving reaction is exothermic See the solution process.
The addition of more heat increases temperature inhibits the dissolving reaction since excess heat is already being produced by the reaction. This situation is not very common where an increase in temperature produces a decrease in solubility. But is the case for sodium sulfate and calcium hydroxide. Increase in solubility with temperature: If the heat given off in the dissolving reaction is less than the heat required to break apart the solid, the net dissolving reaction is endothermic.
The addition of more heat facilitates the dissolving reaction by providing energy to break bonds in the solid.
Solubility And Factors Affecting Solubility
This is the most common situation where an increase in temperature produces an increase in solubility for solids. The use of first-aid instant cold packs is an application of this solubility principle.
A salt such as ammonium nitrate is dissolved in water after a sharp blow breaks the containers for each. Hence, the nature of solvent can be seen as one of the prominent factors affecting solubility. The above observation led to the statement that like dissolves like, that is polar solvents will dissolve polar solutes and non-polar solvents dissolve non-polar solutes. Now let us understand the process by which a solid dissolves in a solvent.
Once a solid solute is added to a solvent, the solute particles dissolve in the solvent and this process is known as dissolution. Solute particles in the solution collide with each other and some of these particles get separated out of the solution, this process is called crystallization.
A state of dynamic equilibrium is established between these two processes and at this point, the number of solute molecules entering the solution becomes equal to the number of particles leaving the solution. As a result, the concentration of the solute in the solution will remain constant at given temperature and pressure. A solution in which no more solute can dissolve in the solvent at a given temperature and pressure is said to be a saturated solution as the solution contains the maximum amount of solute.
The concentration of solute in such a solution is called its solubility at that temperature and pressure. If more solute can be added to a solution then it is called an unsaturated solution.
Apart from the nature of solute and solvent, temperature also affects solid solubility considerably. If the dissolution process is endothermic then the solubility should increase with an increase in temperature in accordance with Le Chateliers Principle.
If the dissolution process is exothermic the solid solubility should decrease. Solid solubility hardly gets affected by changes in pressure. This is due to the fact that solids and liquids are highly incompressible and practically do not get affected by changes in pressure.
Gases In Liquids Gas solubility in liquids deals with the concept of gas dissolving in a solvent. Let us first define solubility. For any substance, solubility is the maximum amount of solute that can be dissolved in a given solvent at a particular temperature. Now our concern is gas solubility in liquids. The gas solubility in liquids is greatly affected by temperature and pressure as well as the nature of the solute and the solvent.
Solubility — Gases in Liquids There are many gases that readily dissolve in water, while there are gases that do not dissolve in water under normal conditions. Oxygen is only sparingly soluble in water while HCl or ammonia readily dissolves in water.
Factors Affecting Solubility Effect of Pressure: It has been found that the gas solubility in liquids increases with increase in pressure.
Effects of Temperature and Pressure on Solubility
To have a better understanding of the effect of pressure on gas solubility let us consider a system of a gas solution in a solvent in a closed container in a state of dynamic equilibrium.
Now the solution is in equilibrium and hence the rate of gaseous molecules entering the solution is equal to the rate of gaseous molecules leaving the solution. Now suppose we increase the pressure of the system by compressing the gas molecules present in the solution.
As a result of an increase in pressure, the gases molecules will now be concentrated in a smaller volume. This will result in an increase in the number of gas molecules per unit volume available above the solution. Since the number of gas molecules presents above the solution has increased, the rate with which the gas molecules will be entering the solution will also increase. The end result is an increase in the number of gas molecules in the solution until a new equilibrium point is attained.
Thus the solubility of gases increases with an increase in the pressure of a gas above the solution. The solubility of a gas in a liquid is directly proportional to the partial pressure of the gas present above the surface of liquid or solution.