Introduction to Solubility Curve
Solubility curve is basically a data-based curve that is going to inform you about the amount of solute that will dissolve in a given amount of solvent at different temperatures. The most typical graphs or solubility curves are the ones that are based on the solid and gaseous solutes that are particularly dissolved in 100 grams of water.
What is Solubility?
Solubility is known as the maximum amount of solute which will dissolve in a given amount of solvent at a specific given temperature and pressure.
There are three different kinds of solutions which will result depending on how much of a particular solute is dissolved in the solvent.
As explained above, the solubility curve is the comparison of the amount of solute dissolved in a given amount of solvent at different temperatures. Here in this article,you will learn about the solubility curve in detail, which will provide you with all the basic information, including solubility rules chart, definition of solubility curve, graph of solubility, some problems of solubility curve and the main that is the importance if this solubility curve.
Solubility Curve Definition
The solubility curve definition chemistry is given as below:
The variation in the solubility of a given substance with the change of temperature is presented by the solubility curve. The solubility curve is the curved line that is drawn on the graph that shows the relationship between the temperature and the solubility of the substance at varying temperatures.
The graphical relationship between the solubility and the temperature is known as the solubility curve. The solubility curve determines the changes of the solubility of a solid at variable temperatures in a solvent. On the graph, the variations in temperature are to be plotted on the x-axis and the solubility is plotted on the y-axis. Temperature plays an important role in solubility since the solubility of a given substance is different at varying temperatures.
Solubility Graph
Let us now look at how the solubility graph looks. The solubility graph is shown as follows:
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How to read the Solubility Curve?
The solubility curve line shows you with a saturated solution. Saturated solution is basically the one with a full dissolved volume of solute in 100 grams of water. Any sim below this line is going to indicate the unsaturated solution. And all the solutions above this line shows you about the supersaturated solution.
Unsaturated Solution: An Unsaturated solution is the one that contains less amount of solute as compared to the maximum amount of solute that is capable of being dissolved for forming a solution. If more solute is added and it does not dissolve then the original solute is saturated and if more solution is added and it is dissolved then the original solution is considered to be an unsaturated one that is going to be shown below the line of solubility curve.
Supersaturated Solution: A chemical solution is considered as the supersaturated one only when the concentration of the solute in the solution exceeds the concentrations that is specified by the value equilibrium solubility. A supersaturated solution is basically in the metastable state. Any supersaturated solution can be brought back to its normal equilibrium state by forcing the excess solution to remove or separate from the solution.
Solubility Rules Chart
The general rules of solubility are given below. Let us look at each one of them and what they are.Most of the chloride salts are soluble. However, there are some exceptions like \[PbCl_{2}\], \[Hg_{2}Cl_{2}\] and \[AgCl\] .
The salts of \[Na^{+}, K^{+}\] and \[NH_{4}^{+}\] are all soluble.
All the sulfate salts are soluble. However, there are some exceptions which include \[BaSO_{4}, CaSO_{4}\] and \[PbSO_{4}\].
Almost all the nitrate (\[NO^{3-}\]) salts are soluble.
Almost all the hydroxide compounds are hardly soluble. The important exceptions in this category are NaOH and KOH. Barium hydroxide and calcium hydroxide, however, are moderately soluble.All the salts of sulfide, phosphate and carbonate are hardly soluble.
Importance of Solubility Curve
The solubility curve is used for determining the amount of substance that is deposited when the solution is cooled. Solubilities of different substances at a given temperature can be determined. The importance of solubility curves is discussed as follows.
Firstly, the solubility curve will help you to predict which substance crystallizes first from the solutions containing two or more solutes. Depending upon their solubility in the solution,
If you are given a substance whose solubility you need to find at a particular temperature then this solubility curve helps you.
There is a particular solubility process for every substance at different temperatures and this curve is going to help you to find the solubility process of a substance at a given temperature.
At a particular temperature if you are provided with a different number of substances then this solubility curve will help you to find the solubility at the same temperature.
This solution will not only provide you information about the saturation of a given substance but heside this it also provides with the information of supersaturated and unsaturated solution.
It gives you a clear idea of the fact that the solubility of a given substance changes with the temperature.
Solubility Curve Problems
Let us now look at some of the solubility curve problems in detail and how to solve them.
Example:
A solution with a precipitate of AgCl in equilibrium consists of \[1.0 \times 10^{-3}\] mol of \[Ag^{+}/L\] and \[1.3 \times 10^{-5}\] mol of \[Cl^{-}/ L\]. determine the solubility product of \[AgCl\].
Solution: The solubility product as per the definition is the product of the concentrations of the ions that are in equilibrium with the precipitate of a sparingly soluble substance.
For \[AgCl\],
\[K_{sp} = [Ag^{+}][Cl^{-}]= (1.0 \times 10^{-3}) ( 1.3 \times 10^{-5})= 1.3 \times 10^{-15}\]
Conclusion
Vedantu has covered all the aspects of solubility curve with examples. You can practice these examples to understand practically.
FAQs on Solubility Curve
1. What is a solubility curve?
A solubility curve is a graph that illustrates the relationship between the solubility of a substance (the solute) and the temperature of the solvent. Typically, the y-axis represents the mass of solute that can dissolve in a fixed amount of solvent (e.g., 100g of water), while the x-axis represents the temperature. This curve visually shows how solubility changes as temperature changes.
2. How does a solubility curve represent saturated, unsaturated, and supersaturated solutions?
A solubility curve provides a clear visual distinction between different types of solutions at various temperatures:
- On the curve: Any point located directly on the line indicates a saturated solution. This is the maximum amount of solute that can be dissolved at that specific temperature.
- Below the curve: A point in the area below the line represents an unsaturated solution, meaning more solute can still be dissolved in the solvent at that temperature.
- Above the curve: A point above the line signifies a supersaturated solution. This is an unstable state where more solute is dissolved than is normally possible at that temperature, often achieved by cooling a saturated solution carefully.
3. What is the practical importance of a solubility curve?
Solubility curves are highly important in both laboratory and industrial settings for several reasons. They allow chemists and engineers to:
- Predict the precise amount of solute that will crystallise or precipitate out of a solution when it is cooled.
- Determine the conditions needed to create a saturated solution for chemical reactions or product formulation.
- Compare the solubilities of different substances at a specific temperature.
- Develop purification techniques for substances through fractional crystallisation.
4. What are the key factors that affect the solubility of a substance?
The solubility of a substance is primarily influenced by four key factors:
- Temperature: For most solid solutes, solubility increases as temperature increases. For all gases, solubility decreases as temperature rises.
- Polarity: The principle of "like dissolves like" is fundamental. Polar solutes (like sugar) dissolve well in polar solvents (like water), whereas non-polar solutes (like oil) do not.
- Pressure: This factor significantly affects the solubility of gases in liquids. According to Henry's Law, increasing the pressure of a gas above a liquid increases its solubility.
- Molecular Size: For solutes with similar properties, smaller molecules tend to dissolve more readily than larger ones.
5. How can you use a solubility curve to determine the amount of solute that will crystallise out when a solution is cooled?
To calculate the mass of solute that crystallises upon cooling, you can follow these steps using the curve:
1. Find the initial high temperature on the x-axis and read its corresponding solubility value on the y-axis. This is the initial amount of dissolved solute.
2. Find the final lower temperature on the x-axis and read its corresponding solubility value.
3. Subtract the solubility at the final temperature from the solubility at the initial temperature. The result is the mass of solute that will precipitate or crystallise out of the solution.
6. Why do the solubility curves for gases slope downwards with increasing temperature?
The solubility of gases in liquids decreases as temperature rises because the dissolution process for a gas is typically exothermic (it releases heat). According to Le Chatelier's principle, when heat is added to an exothermic system (by increasing the temperature), the equilibrium shifts to counteract the change. In this case, it shifts to favour the reactants (the undissolved gas and solvent), causing the gas to escape the solution and thus decreasing its solubility.
7. What is the difference between the solubility curve of a substance like potassium nitrate (KNO₃) and sodium chloride (NaCl)?
The main difference lies in how their solubilities are affected by temperature:
- Potassium Nitrate (KNO₃): The solubility of KNO₃ increases dramatically as temperature rises. This is represented by a steeply upward-sloping curve, indicating a high sensitivity to temperature changes.
- Sodium Chloride (NaCl): The solubility of NaCl (common salt) increases only very slightly with a rise in temperature. This results in a curve that is nearly flat, showing that temperature has a minimal effect on how much salt can dissolve in water.
8. What information can you get from a point that lies exactly on the solubility curve?
A point located exactly on a solubility curve represents a state of dynamic equilibrium in a saturated solution. This means that the rate at which the solute is dissolving into the solvent is perfectly balanced by the rate at which the dissolved solute is crystallising back into its solid form. While the overall concentration remains constant, the solution is not static; particles are continuously transitioning between the dissolved and undissolved states.
