Ion exchange reactions are processes that occur between complex substances. They should be accompanied by the appearance of a certain result: precipitation, evolution of a gaseous compound, and the formation of a little dissociable substance (for example, water).
Reaction concept
The course of organic chemistry examines the interactions between the compounds that are necessary for human and animal life: proteins, fats, carbohydrates. Chemical processes are usually called such processes that occur between substances with the receipt of other compounds that differ from the original in properties and composition.
Ion exchange reactions are a typical example of chemical processes, since they are accompanied by a change in color, the appearance of gas, and precipitation.
The reagents are the source compounds, and the products are the final compounds.
The driving force of the process is the nature of the reagents, product features, concentration of reacting components, temperature, pressure.
Interaction Features
Ion exchange reactions are the interaction between substances taken in solutions. Like any other processes of a chemical nature, they occur with the release or absorption of heat, a change in color, state of aggregation.
Translated from the Latin language, “reaction” means “retaliatory action, rebuff”.
That is why ion exchange reactions are the response of some substances to the attack of others.
Flow conditions
Among those factors that are necessary for chemical interaction, there are:
- reacting compounds should be in maximum contact;
- in some cases, an increase in temperature is required;
- part of the interactions is possible only when exposed to electricity or ultraviolet radiation.
Reaction classification options
It is difficult to combine all processes accompanied by changes in the composition and properties of compounds into one classification.
Whenever possible processes in the forward and reverse direction, inorganic and organic processes are divided into two groups.
The ion exchange reaction between solutions of soluble compounds irreversibly occurs when an insoluble product forms between them. This is used in analytical chemistry for the qualitative determination of cations (anions) in a mixture of solutions.
For example, a solution containing a sulfate anion (SO 4 2- ) is used to detect barium cations (Ba 2+ ).
Example of ionic equations accompanied by precipitation
How to correctly equate the processes characteristic of this case? Consider the reduced ionic equations as an example of this ion exchange reaction. This issue is included in the school curriculum, therefore, it deserves close consideration.
The first step is to write the process in molecular form.
BaCl2 + Na 2 SO 4 = BaSO 4 + 2NaCl
To understand whether the ion exchange reaction between solutions of these substances really takes place irreversibly, a table of the solubility of acids, salts, and bases will be required. One of the products is barium sulfate (middle salt), which is an insoluble compound. Therefore, the process is really irreversible, accompanied by precipitation.
The second step is to write the complete ionic equation. Each of the starting compounds, the products of the interaction is recorded in the form of cations and anions.
Ba 2+ + 2Cl - + 2Na + + SO 4 2- = BaSO 4 + 2Na + + 2Cl -
On the left and right sides of this equation are positive and negative ions that are not bound to a precipitate, a slightly dissociable or gaseous compound. After their reduction, we obtain a variant of the short ionic equation.
Ba 2+ + SO 4 2- = BaSO 4
Gas Generation Process Example
When else can ion exchange reactions occur? Examples with a solution involving the formation of a gaseous substance are given for carbonate. A qualitative reagent for the anion CO32- is the interaction with hydrogen cations. The result of the process is the formation of carbon dioxide.
Imagine the interaction in molecular and ionic form.
Na 2 CO 3 + 2HCl = 2NaCl + CO 2 + H 2 O
The reaction products are carbon dioxide and water, which do not decay into ions. Imagine the interaction in full ionic form.
2Na + + CO 3 2- + 2H + + 2Cl - = 2Na + + 2Cl - + CO 2 + H 2 O
After the reduction of ions repeating in the left and right parts, we obtain the following form of this process:
CO 3 2- + 2H + = CO 2 + H 2 O
Obtaining a slightly dissociable compound
What other signs may be accompanied by ion exchange reactions? We give examples with a solution for the classical process of neutralization between a solution of alkali and acid.
The interaction of a solution of hydrochloric acid with sodium hydroxide is accompanied by the formation of water (a slightly dissociable compound). You can check the completeness of the process using the indicator. If you initially add an alcohol solution of phenolphthalein to the alkali, as the hydrochloric acid is added to it, the color will disappear (neutralization is in progress).
In molecular form, the process is as follows:
NaOH + HCl = NaCl + H 2 O
A brief ionic equation reflects the neutralization process:
OH - + H + = H2O
Conclusion
Unlike other types of chemical processes, ion exchange occurs only between solutions of complex compounds. Also among the prerequisites that are associated with similar processes, we note their irreversibility. In cases where among the products there is a slightly dissociable compound, a gaseous substance, a precipitate, then we can talk about the completeness of the process.
If, in the case of substitution, the oxidation states of compounds change, in the case of ion exchange, the valence state of atoms does not change. Such processes occur between complex substances: salts, acids, bases, oxides.
A special case of such interactions is the neutralization between alkali and acid. They obey the laws of chemical equilibrium, go in the direction where one of the compounds is removed from the reaction sphere in a volatile, gaseous form, or as a slightly dissociable substance.
A chemical reaction is a complex process, which involves the conversion of some substances into others, which differ from the original in structure, composition. Only in the presence of one of the three features listed above can we talk about the completeness of the interaction.