A solution is another name because that a homogeneous mixture. A mixture together a material composed of two or an ext substances. In a solution, the mix is so intimate that the different substances cannot be identified by sight, even with a microscope. Compare, because that example, a mixture of salt and also pepper and another mixture consists of salt and also water. In the an initial mixture, we have the right to readily see individual seed of salt and the flecks the pepper. A mixture of salt and also pepper is no a solution. However, in the second mixture, no matter how carefully we look, us cannot watch two different substances. Salt liquified in water is a solution.

You are watching: Salt dissolved in water is a solution therefore

The significant component the a solution, referred to as the solvent, is typically the same phase together the systems itself. Every minor ingredient of a systems (and there might be an ext than one) is dubbed the solute. In many of the services we will describe in this textbook, there will certainly be no ambiguity about whether a ingredient is the solvent or the solute. For example, in a systems of salt in water, the solute is salt, and also solvent is water.

Solutions come in every phases, and the solvent and the solute carry out not need to be in the same phase to type a systems (such together salt and also water). For example, wait is a gaseous systems of around 80% nitrogen and around 20% oxygen, v some other gases existing in lot smaller amounts. An alloy is a solid solution consisting the a metal (like iron) v some other steels or nonmetals liquified in it. Steel, an alloy of iron and carbon and little amounts of other metals, is an example of a solid solution. Table (PageIndex1) lists some common varieties of solutions, with instances of each.

Table (PageIndex1): types of remedies Solvent PhaseSolute PhaseExample
gas gas air
liquid gas carbonated beverages
liquid liquid ethanol (C2H5OH) in H2O (alcoholic beverages)
liquid solid saltwater
solid gas H2 gas took in by Pd metal
solid liquid Hg(ℓ) in dentist fillings
solid solid steel alloys

What reasons a equipment to form? The simple answer is that the solvent and the solute need to have comparable intermolecular interactions. Once this is the case, the individual particles of solvent and also solute can easily mix so intimately the each particle of solute is surrounded by particles of solute, developing a solution. However, if two substances have really different intermolecular interactions, huge amounts of power are required to pressure their individual corpuscle to mix intimately, for this reason a systems does no form. Hence two alkanes like n-heptane, C7H16, and n-hexane, C6H14, are totally miscible in all proportions. The C7H16 and C6H14 molecules are so comparable (recall ar 4.6) the there are just negligible differences in intermolecular forces.

For a similar reason, methanol, CH3OH, is completely miscible with water. In this instance both molecules room polar and can kind hydrogen bonds among themselves, and also so there are strong intermolecular attractions within every liquid. However, CH3OH dipoles have the right to align v H2O dipoles, and also CH3OH molecules can hydrogen bond come H2O molecules, and so the attractions amongst unlike molecule in the systems are comparable to those amongst like molecule in each pure liquid.

This procedure leads to a an easy rule that thumb: like dissolves like. Solvents the are very polar will certainly dissolve solutes that are very polar or also ionic. Solvents that are nonpolar will certainly dissolve nonpolar solutes. Hence water, being polar, is a good solvent for ionic compounds and also polar solutes choose ethanol (C2H5OH). However, water does not dissolve nonpolar solutes, together as numerous oils and greases (Figure (PageIndex1)).

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Figure (PageIndex1): A beaker hold water with blue food dye (upper liquid layer) and a much an ext dense perfluoroheptane (a fluorocarbon) reduced liquid layer. The two fluids cannot mix and the dye can not dissolve in fluorocarbon. A goldfish and also a crab have actually been introduced right into the water. The goldfish cannot penetrate the dense fluorocarbon. The crab floats in ~ the liquid boundary with only parts of his foot penetrating the fluorocarbon fluid, unable to sink to the bottom that the beaker. 4 minutes 1 coins remainder on the bottom the the beaker. Pets were rescued from their predicament ~ the picture was taken. Figure used through permission from Wikipedia (Sbharris (Steven B. Harris)).

We use words soluble to define a solute that dissolves in a particular solvent, and the word insoluble because that a solute the does not dissolve in a solvent. Thus, us say that sodium chloride is soluble in water however insoluble in hexane (C6H14). If the solute and the solvent room both liquids and soluble in any kind of proportion, us use the word miscible, and the indigenous immiscible if they space not.




Example (PageIndex2)

Predict i beg your pardon of the adhering to compounds will be most soluble in water:

(underset extEthanolmathop extCH_ ext3 extCH_ ext2 extOH,) (underset extHexanolmathop extCH_ ext3 extCH_ ext2 extCH_ ext2 extCH_ ext2 extCH_ ext2 extCH_ ext2 extOH,)

Solution

Since ethanol contains an OH group, it have the right to hydrogen bond to water. Although the very same is true the hexanol, the OH group is found only at one end of a fairly huge molecule. The rest of the molecule can be intended to behave lot as despite it were a nonpolar alkane. This substance should thus be much much less soluble than the first. Experimentally we uncover that ethanol is fully miscible v water, while just 0.6 g hexanol disappear in 100 g water.

See more: The Refinement Of Whole Grains Transforms Brown Rice Into White Rice.


Exercise (PageIndex2)

Would I2 be an ext soluble in CCl4 or H2O?

Answer

I2 is nonpolar. Of the two solvents, CCl4 is nonpolar and H2O is polar, therefore I2 would be meant to be more soluble in CCl4.