# Electrolyte and Nonelectrolyte Solutions

## Electrolytes contain dissolved ions that enable them to conduct electricity, while non-electrolytes don't easily conduct electricity.

#### Key Points

• When a salt, acid, or base dissolved in a solvent, the resulting dissociation of the molecules into ions forms a solution that is able to conduct electricity. This is called an electrolyte solution.

• When a solute dissolved in a solvent to form a solution, it is possible for the solute to dissociate into ions. These ions will affect the overall concentration of species in solution. Take care to note how many ions each solute molecule forms.

• Nonelectrolyte solutions do not conduct electricity. They are still solutions containing solutes and solvents, but the solute molecules do not dissociate into ions, preventing conductivity.

#### Terms

• A homogeneous mixture, which may be liquid, gas or solid, formed by dissolving one or more substances.

• An ionic compound that is composed of cations and anions The product is electrically neutral. The two ions are held together by ionic bonds, not covalent bonds.

• Any substance that is dissolved in a liquid solvent to create a solution.

• A substance that does not dissociate into ions when in solution, and therefore is a poor conductor of electricity when in solution

#### Examples

• One relevant example of an electrolyte solution is sports drinks, often advertised as containing "replacement electrolytes." When humans sweat, we lose ions necessary for vital bodily functions. We must replenish them by consuming more ions, often in the form of an electrolyte solution.

#### Figures

1. ##### Preparing a Solution

As the solute dissolves, the mixture becomes a solution and turns clear.

### Electrolyte Solutions

An electrolyte is a solution that is able to conduct electricity. To meet this criteria, a solution must contain ions. Commonly, electrolyte solutions contain acids, bases, or salts as their ionic solute. Electrolyte solutions are normally formed when a salt is placed into a solvent such as water. The individual components dissociate due to the thermodynamic interactions between the solvent and solute molecules in a process called solvation. For example, when table salt, NaCl, is placed in water, the salt (a solid) dissolves into its component ions, according to the dissociation reaction:

NaCl(s) → Na+(aq) + Cl(aq)

It is also possible for substances to react with water to produce ions. For example, carbon dioxide gas dissolves in water to produce a solution which contains hydronium, carbonate, and hydrogen carbonate ions. To determine the concentration of a dissolved species in a solution, one must consider the number of moles of ions formed per mole of solute added. For example, one mole of sodium chloride dissolved in one liter of water produces a solution that is two molar in ions, as it contains one mole of sodium ions and one mole of chloride ions. For a species such as magnesium bromide, MgBr2, one mole of solute will produce three moles of dissolved ions.

When solutes dissociate (or if a molecule ionizes), the solution can conduct electricity. Compounds that readily form ions—making them good conductors—are known as strong electrolytes. If only a small amount of ions are formed, electricity is poorly conducted, and the compound is known as a weak electrolyte. A strong electrolyte will dissolve completely and all ions will dissociate. A weak electrolyte, on the other hand, will partially dissociate, but some ions will remain bonded together. An example of a weak electrolyte is acetic acid, which only forms acetate anions and hydronium cations to a small extent.

Figure 1

### Nonelectrolyte Solutions

Nonelectrolytes are solutions which cannot readily conduct electricity. The solute molecules are typically held together by covalent rather than ionic bonds. This leads to an inability to dissociate when dissolved. These solutions exhibit the normal effects of boiling-point elevation and freezing-point depression. For purposes of determining concentration, one mole of solute remains one mole after being dissolved in the solvent.

#### Key Term Glossary

acid
an electron pair acceptor; generally capable of donating hydrogen ions
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anion
A negatively charged ion, as opposed to a cation
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base
A proton acceptor, or an electron pair donor.
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Boiling
Boiling is the rapid vaporization of a liquid and occurs when a liquid is heated to its boiling point. A liquid's boiling point is the temperature at which the vapor pressure of the liquid is equal to the pressure exerted on the liquid by the surrounding environment.
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boiling point
the temperature at which a liquid boils, with the vapor pressure equal to the given external pressure
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boiling point elevation
the phenomenon that the temperature at which a substance's vapor pressure equals the external pressure increases when another compound is added
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bond
a link or force between neighboring atoms in a molecule
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carbonate
Any salt or ester of carbonic acid
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cation
A positively charged ion, as opposed to an anion.
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compound
A substance made from any combination elements.
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concentration
the proportion of a substance in a mixture
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conductor
something that can transmit electricity, heat, light, or sound
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covalent
Characterized by shared pairs of electrons between atoms.
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dissociation
Referring to the process by which compounds split into smaller constituent molecules, usually in a reversible manner.
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electrolyte
a substance that, in solution or when molten, ionizes and conducts electricity
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Freezing
Freezing or solidification is a phase transition in which a liquid turns into a solid when its temperature is lowered below its freezing point.
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freezing point
The temperature at which a liquid freezes, and the solid and liquid phases are in equilibrium; normally the same as the melting point.
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freezing point depression
the phenomenon that adding a solute to a solvent decreases the temperature at twhich the liquid solvent becomes a solid.
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gas
Matter in a state intermediate between liquid and plasma that can be contained only if it is fully surrounded by a solid (or held together by gravitational pull); it can condense into a liquid, or can (rarely) become a solid directly.
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hydronium
The hydrated hydrogen ion, $H_3O^+$.
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ion
An atom or group of atoms bearing an electrical charge, such as the sodium and chlorine atoms in a salt solution.
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ionic
of, relating to, or containing ions
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ionic bond
A type of chemical bond where two atoms or molecules are connected to each other by electrostatic attraction.
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liter
a non-SI metric system unit of volume equal to 1 cubic decimeter (dm^3), 1,000 cubic centimeters (cm^3) or 1/1,000 cubic meter (m^3)
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mole
In the International System of Units, the base unit of the amount of substance; the amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kg of carbon-12. Symbol: mol. The number of atoms in a mole is known as Avogadro’s number.
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molecule
the smallest particle of a specific element or compound that retains the chemical properties of that element or compound; two or more atoms held together by chemical bonds
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nonelectrolyte
A substance that does not dissociate into ions when in solution, and therefore is a poor conductor of electricity when in solution
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salt
An ionic compound that is composed of cations and anions The product is electrically neutral. The two ions are held together by ionic bonds, not covalent bonds.
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solid
A substance in the fundamental state of matter that retains its size and shape without need of a container (as opposed to a liquid or gas).
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solute
Any substance that is dissolved in a liquid solvent to create a solution.
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solution
A homogeneous mixture, which may be liquid, gas or solid, formed by dissolving one or more substances.
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Solution
A homogeneous mixture, which may be liquid, gas or solid, formed by dissolving one or more substances.
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solvent
a substance that dissolves a solute, resulting in a solution
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substance
Physical matter; material.
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thermodynamics
The science of the conversions between heat and other forms of energy.