What Is A Double Replacement

Double Replacement Reaction - Double Displacement Reaction — The cations and anions of 2 compounds switch places to form two new products in a double replacement or double displacement reaction.

A double replacement reaction is a type of chemical reaction where two reactants exchange ions to form 2 new products with the same blazon of chemic bonds. Usually, one of the products forms a precipitate. Double displacement reactions take the course:

AB + CD → AD + CB

Double replacement reactions may involve reactants that incorporate either ionic or covalent bonds, but the blazon of reaction is more common with ionic compounds. Acids and bases may participate in double replacement reactions. Usually, the solvent is water.

Alternating Names

Other names for a double replacement reaction are a double displacement reaction, exchange reaction, or salt metathesis reaction. A double replacement reaction is called a double decomposition reaction, but the term is reserved for when one or both of the reactants doesn't dissolve in a solvent.

Double Replacement Reaction Examples

An example of a double replacement reaction is the reaction between argent nitrate and sodium chloride in water. Both silver nitrate and sodium chloride are ionic compounds. Both reactants dissolve into their ions in aqueous solution. The silver ion picks up the sodium's chloride ion to form silver chloride, while the sodium ion picks upwards the nitrate anion to form sodium nitrate. Like the reactants, both products are ionic compounds. Silver chloride has a depression solubility in water, so it precipitates out of solution.

AgNO₃ + NaCl → AgCl + NaNO₃

Another example is the reaction between barium chloride and sodium sulfate to form barium sulfate and sodium chloride:

BaCl_two(aq) + Na₂So₄(aq) → BaSO₄(s) + 2 NaCl(aq)

All of the reactants and products contain ionic bonds. The product barium sulfate precipitates out of solution as a solid.

How to Recognize a Double Replacement Reaction

You lot tin recognize a double replacement reaction in a chemic equation by checking whether the cations exchange anions with each other. If u.s. of thing of the reactants and products are listed, expect for a reaction betwixt two aqueous solutions that yields one aqueous production (aq) and i that precipitates to course a solid product (due south). If you don't know the reactants but you see precipitate formation upon mixing them, suspect a double replacement reaction.

If you lot tin can't visually discover the reaction, yous tin can predict whether or non the reactants will dissolve and a precipitate will form (indicating a double replacement reaction) using solubility rules.

Types of Double Replacement Reactions

There are several categories of double replacement reactions, including neutralization, alkylation, acid-carbonate reactions, counter-ion exchange, aqueous metathesis with precipitation (precipitation reactions), and aqueous metathesis with double decomposition (double decomposition reactions). Nonetheless, the two types near often seen in general chemical science are neutralization reactions and precipitation reactions.

A neutralization reaction is a double deportation reaction between acids and bases. When water is the silver, the reaction commonly produces an ionic chemical compound—a salt. If one or both of the reactants is a strong acrid or strong base, the reaction gain in the forward direction.

The reaction between hydrofluoric acid and sodium hydroxide in water to course water and sodium fluoride is an example of a neutralization reaction. Hydrofluoric acid is (naturally) an acid, while sodium hydroxide is a base. The general form of the reaction is:

acid + base → water + common salt

In this instance, the reaction is:

HF(aq) + NaOH(aq) → H_twoO + NaF(aq)

Another example of a neutralization reaction is the reaction between baking soda and vinegar in the baking soda volcano. The reaction ultimately produces a gas (carbon dioxide) and a salt (sodium carbonate), but the initial neutralization reaction forms carbonic acid (H₂CO₃) and sodium acetate (NaCH₃COO)

NaHCO₃ + CH₃COOH(aq) → H₂CO₃ + NaCH_iiiCOO

The cations exchange anions, but it's trickier to notice the swap because of the mode the compound formulas are written. You can place the reaction equally double replacement when y'all compare the atoms in the anions of the reactants and products.

In a precipitation reaction, two aqueous ionic compounds class an insoluble ionic product. An example is the reaction between lead(Ii) nitrate and potassium iodide to form potassium nitrate and (insoluble) lead iodide.

Pb(NO_iii)₂(aq) + 2 KI(aq) → 2 KNO₃(aq) + PbI₂(s)

You can recognize precipitate formation because of the (s) following the chemic formula. While lead iodide is the precipitate, the solvent (water) and soluble reactants and production are called the supernate or supernatant. Precipitate germination drives the reaction in the frontward direction, every bit product leaves solution.

References

Dilworth, J. R.; Hussain, W.; Hutson, A. J.; Jones, C. J.; Mcquillan, F. S. (1997). "Tetrahalo Oxorhenate Anions." Inorganic Syntheses. 31: 257–262. doi:10.1002/9780470132623.ch42
IUPAC (1997). "Metathesis." Compendium of Chemic Terminology (2nd ed.) (the "Gilt Book"). doi:10.1351/goldbook.M03878
March, Jerry (1985).Advanced Organic Chemistry: Reactions, Mechanisms, and Construction (3rd ed.). New York: Wiley. ISBN 0-471-85472-7.
Myers, Richard (2009).The Nuts of Chemistry. Greenwood Publishing Group. ISBN 978-0-313-31664-seven.