In chemistry, a solute is the substance dissolved in a solvent or the part of a chemical solution present in the smaller amount. Mixing a solute and a solvent resulting in dissolving the solute, which is also known as solvation. Concentration describes the amount of solute in a solvent or solution. For example, the concentration 0.1M HCl describes a solution consisting of 0.1 moles of hydrochloric acid per liter of solution.
The term “solute” comes from the Latin word solvere, which means “to loosen.” The words “solvent” and “dissolve” also derive from the same word.
While solutes are most often discussed in liquid solutions, they also occur in gases and solids.
A solute displays characteristic properties in a solution:
- The distribution of a dissolve solute is homogeneous. That is, the number of solute particles per volume is the same, no matter where a solution is sampled.
- Solute particles are not visible to the eye.
- The solute in a solution does not scatter light.
- Solute particles do not settle out of solution and cannot be separated from a solution by filtration.
- In a solution, the solute is in the same phase as the solvent.
How to Tell Which Is Solute and Which Is Solvent
The solute is the part of a solution present in a lower amount than the solvent. If you know the composition of the solution, it’s easy to identify the solvent, since it accounts for the largest fraction. The remainder of the solution consists of the solute. There may be more than one solute in a solution.
In a chemical reaction, the solute is present in a smaller mole fraction and dissolves in the solvent. Any time you see the symbol (aq) following a chemical species, you know it is a solute in aqueous solution (water).
Here are examples of solutes:
|Solute||Solution||Type of Solution||Solvent|
|Salt||Seawater||Solid dissolved in liquid||Water|
|Sugar, dissolved carbon dioxide||Soda||Solid and gas dissolved in liquid||Water|
|Oxygen, water vapor, carbon dioxide, argon||Air||Gas dissolved in gas||Nitrogen|
|Chromium||Stainless Steel||Solid dissolved in solid||Iron|
|NaOH (sodium hydroxide)||1.0M NaOH (aq)||Solid dissolved in liquid||Water|
|Ethanol||Beer||Liquid dissolved in liquid||Water|
|Acetic acid||Vinegar||Liquid dissolved in liquid||Water|
|Ethane, propane, butane||Natural gas||Gas dissolved in gas||Methane|
|Silver, copper, indium||Dental amalgam||Solid dissolved in solid||Mercury|
Predicting Whether a Solute Will Dissolve
Solubility is a measure of how much of a solute will dissolve in a solvent. Generally, polar solvents dissolve polar solutes, while nonpolar solvents dissolve nonpolar solutes. For example, salt (polar) dissolves in water (polar), but not in oil (nonpolar). Solubility depends on several factors, including temperature, pressure, and the presence of other substances. For example, more salt will dissolve in boiling water than in ice water.
- Clugston, M.; Fleming, R. (2000). Advanced Chemistry (1st ed.). Oxford: Oxford Publishing.
- Hefter, G.T.; Tomkins, R.P.T (ed.) (2003). The Experimental Determination of Solubilities. Wiley-Blackwell. ISBN 978-0-471-49708-0.
- Houk, C.; Post, R. (eds.) (1997). Chemistry, Concept and Problems. John Wiley & Sons. ISBN 978-0-471-12120-6.
- IUPAC (1997). “Solute.” Compendium of Chemical Terminology (2nd ed.) (the “Gold Book”). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications. Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. doi:10.1351/goldbook