Chem 2 - Introduction to Solutions I
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A solution is a homogeneous mixture of two or more substances. It consists of a solute dissolved in a solvent. Solutions can be mixtures of solids, liquids, or gases. Water is an excellent solvent due to its polar nature and ability to hydrogen bond. The formation of a solution is a physical process based on the tendency toward mixing and a match between the intermolecular forces of the solute and solvent. If these forces are similar, mixing will occur spontaneously to form a solution.
Chem 2 - Introduction to Solutions I
- 1. Introduction to Solutions Pt. 1 By Shawn P. Shields, Ph.D. This work is licensed by Shawn P. Shields-Maxwell under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
- 2. Solutions Generally, a solution is a stable homogeneous mixture of two or more substances. Recall: “Homogeneous” means uniform throughout the mixture. Other features of solutions: Solute particles cannot be differentiated by the eyes, nor do they scatter light. The mixture cannot be separated by filtration.
- 3. Recall: Overview of Solution Terms The substance dissolved in another substance is called the solute. The solvent is the substance in which the solute is dissolved. The concentration of a solution is a measure of the amount of solute dissolved in solution. “Solute”
- 4. Solutions Solutions can be mixtures of solids, liquids, and gases. One common “solution” is a solute, such as NaCl, dissolved in water. A “solid solution” is a homogeneous mixture of two solids (often metals forming alloys). Two (or more) liquids can also form a solution, as well as a gas dissolved in a liquid.
- 5. Aqueous Solutions In the picture, sugar is added to water and stirred. Once the sugar dissolves, a solution of sucrose in water is formed.
- 6. Recall: Water as the Solvent Water is an excellent solvent due to its polar nature and ability to hydrogen bond. “Partial charges” on H2O molecules are attracted to each other and to ions or polar molecules in solution. “partial charges” +
- 7. Solution Formation The formation of a solution is a physical process (as opposed to chemical). Solutions form based on two factors: The tendency toward mixing (increased entropy) The “match” between the intermolecular forces for the solute and the solvent.
- 8. IM Forces and Solution Formation Let’s look at two cases: Case 1: The solvent and solute have very different strengths and types of intermolecular forces (e.g., oil has (mainly) dispersion forces and water can hydrogen bond ). No mixing occurs. Even if the mixture is shaken, the two components separate from each other.
- 9. Solution Formation Case 2: The solvent and solute have very similar strengths and types of intermolecular forces (e.g., NaCl and water). Mixing occurs spontaneously. NaCl and water interact through ion-dipole attractions.
- 10. A Few More Terms.. Saturated solutions- The solvent has dissolved the maximum amount of solute that it can hold. Unsaturated solutions- The solvent has not dissolved the maximum amount of solute. Supersaturated solutions- An unstable solution (often) prepared at higher temperatures then cooled. The solvent dissolved more than the maximum amount of solute.
- 11. Next Up… Factors Affecting Solution Formation