In a laboratory setting, in order to make a homogeneous solution, you add the solute in small increments to the solvent, with thorough stirring or agitation of the mixture in each time until the solute is no longer distinguishable from the solvent or until a small amount of undissolved solute remains at the bottom after mixing. Heat may be applied to the solution to speed up the dissolution of the solute, although one risks supersaturating the solution when heat is used.
The molecules making up the solute are expected to disperse at a uniform manner throughout the solvent so a homogeneous solution is formed. Now, for this to happen the interactions between molecules (called intermolecular forces of attraction, or IMF, the strength of which depends on the amount of energy contained in the arrangement of the molecules by virtue of IMFs) binding them together to form the solid or liquid solute must be broken, so that the molecules are free to disperse. Additionally, for ionic solutes and electrolytes like sodium chloride dissolved in solvents like water, the ionic bond, which has an associated bond energy, is broken along with the IMFs. Thus two things can be said to happen to the solute when it dissolves (1) its spatial arrangement in the solution becomes random, or disordered and (2) its energy decreases. The same thing can be said for the solvent its IMFs get broken, and so it becomes more disordered and its energy decreases upon addition of the solute.
All substances dissolve in a given solvent to a particular extent, which is quantified and tabulated in chemistry books and manuals. Ionic compounds and electrolytes are expected to dissolve almost completely in solutions with water as the solvent. Solutes with weak IMFs are likely to dissolve in solution, and solvents with weak IMFs favor the dissolution of solutes. Also, strong interactions between solute and solvent molecules lead to good dissolution.
The molecules making up the solute are expected to disperse at a uniform manner throughout the solvent so a homogeneous solution is formed. Now, for this to happen the interactions between molecules (called intermolecular forces of attraction, or IMF, the strength of which depends on the amount of energy contained in the arrangement of the molecules by virtue of IMFs) binding them together to form the solid or liquid solute must be broken, so that the molecules are free to disperse. Additionally, for ionic solutes and electrolytes like sodium chloride dissolved in solvents like water, the ionic bond, which has an associated bond energy, is broken along with the IMFs. Thus two things can be said to happen to the solute when it dissolves (1) its spatial arrangement in the solution becomes random, or disordered and (2) its energy decreases. The same thing can be said for the solvent its IMFs get broken, and so it becomes more disordered and its energy decreases upon addition of the solute.
All substances dissolve in a given solvent to a particular extent, which is quantified and tabulated in chemistry books and manuals. Ionic compounds and electrolytes are expected to dissolve almost completely in solutions with water as the solvent. Solutes with weak IMFs are likely to dissolve in solution, and solvents with weak IMFs favor the dissolution of solutes. Also, strong interactions between solute and solvent molecules lead to good dissolution.
No comments:
Post a Comment