Introduction to Solutions
A solution is a homogeneous mixture. That means the components of asolution are so evenlyspread throughout the mixture that there are no perceivable differences incomposition. Solutions canbe formed by mixing two substances together such as sugar and water. Ifyou pour a packet of sugarinto a glass of water, initially you have a suspension as the sugarcrystals float about in the glass.When you have stirred the sugar and water for long enough, you willeventually get a clear, colorlessmixture. Some people, especially young children, can be fooled by such ademonstration intothinking that the sugar has “disappeared”. However, as chemists, we knowbetter. The law ofconservation of matter states that the sugar can not just disappear, itmust have gone somewhere else.That somewhere else is into solution. The sugar has become evenlydispersed. In fact the sugarmolecules are so well spread out that we can no longer see a single sugarcrystals. However, if youtaste the water, you will find it to be sugary–confirming the presence ofsugar in the water. Theminor component of the solution is called the solute. In the presentexample, sugar is the solute.The major component of the solution is called the solvent. In thiscase water is the solvent.
You are watching: The minor component in a solution is called the solvent.
Solutions can also be formed by mixing together many different phases ofmatter. For instance, air isa solution. The solute gasses oxygen, carbon dioxide, argon, ozone, andothers are dissolved in thesolvent nitrogen gas. Another example is found in “gold” jewelry. Most ofthe golden jewelry soldin the world is not 24 karat (i.e. 100% pure gold) but rather it is asolution of other metals,commonly silver and copper, in a gold solvent. Such a solution of metal(s)in another metal is calledan amalgam.
The Composition of Solutions
Perhaps the most important property of a solution is its concentration.A dilute acetic acidsolution, also called vinegar, is used in cooking while a concentratedsolution of acetic acidwould kill you if ingested. The only difference between such solutions isthe concentration of thesolute. In order to quantify the concentrations of solutions, chemistshave devised many differentunits of concentration each of which is useful for different purposes.
Molarity, the number of moles of solute per liter of solution, has theunits moles / L which areabbreviated M. This unit is the most commonly used measure ofconcentration. It is usefulwhen you would like to know the number of moles of solute when you knowboth the molarity andthe volume of a solution. For example, it is easy to calculate the volumeof a 1.5 M solutionof HCl necessary to completely react with 0.32 moles of NaOH:
Normality, the number of molar equivalents of solute per liter ofsolution, has the unitsequivalents / L which are abbreviated N. To illustrate thedifference between molarity andnormality let”s assume that we had used a 1.5 M solution of sulfuricacid,H2SO4, instead of a 1.5 M solution ofhydrochloric acid, HCl inthe above example. Because sulfuric acid can donate two protons to theNaOH, as noted in the, it will only take half as much sulfuricacid as hydrochloric acidto neutralize the sodium hydroxide.
In the present example, the 1.5 M solution of sulfuric acid reactslike a 3.0 Msolution of hydrochloric acid because there are two equivalents ofH+ per mole ofsulfuric acid. Therefore, that solution of sulfuric acid is 3.0 N.