A precipitation reaction is a reaction that yields an insoluble product—a precipitate—when two options are mixed. When a colorless systems of silver nitrate is mixed with a yellow-orange solution of potassium dichromate, a red precipitate of silver dichromate is produced.

You are watching: Potassium chromate and silver nitrate balanced equation

< ce AgNO_3(aq) + K_2Cr_2O_7(aq) ightarrow Ag_2Cr_2O_7(s) + KNO_3(aq) label4.2.1>

This unbalanced equation has actually the general type of an exchange reaction:

Thus precipitation reactions are a subclass that exchange reactions that occur in between ionic compounds as soon as one that the commodities is insoluble. Since both components of each compound adjust partners, together reactions are sometimes referred to as double-displacement reactions. Precipitation reactions space usedto isolate metals that have actually been extracted from their ores, and to recover precious steels for recycling.


Video: mixing potassium dichromate and silver nitrate with each other to start a precipitation reaction (Equation ( ef4.2.1)).

Just as vital as predicting the product that a reaction is knowing when a beer-selection.comistry reaction will certainly not occur. Simply mixing solutions of two various beer-selection.comical substances does not guarantee the a reaction will certainly take place. Because that example, if 500 mL that aqueous (NaCl) solution is blended with 500 mL the aqueous (KBr) solution, the final solution has actually a volume of 1.00 L and contains (ceNa^+(aq)), (ceCl^−(aq)), (ceK^+(aq)), and also (ceBr^−(aq)). As you will view in (Figure (PageIndex1)), nobody of these varieties reacts with any kind of of the others. Once these options are mixed, the only effect is come dilute each solution with the other.

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Figure (PageIndex1): The result of mix Aqueous (ceKBr) and (ceNaCl) Solutions. Because no net reaction occurs, the only impact is come dilute each solution with the other. (Water molecules space omitted from molecular views of the solutions for clarity.)

Predicting Precipitation Reactions

A precipitation reaction occurs once a heavy precipitate develops after mixing two strong electrolyte solutions. As stated previously, if no one of the types in the systems reacts then no net reaction occurred.

Predict what will take place when aqueous services of barium chloride and also lithium sulfate space mixed.

Change the partner of the anions and also cations ~ above the reactant next to kind new link (products):

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Because barium chloride and also lithium sulfate are strong electrolytes, every dissociates totally in water to give a solution that contains the ingredient anions and cations. Mix the two services initially gives an aqueous solution that consists of (ceBa^2+), (ceCl^−), (ceLi^+), and (ceSO4^2−) ions. The only feasible exchange reaction is to type (ceLiCl) and also (ceBaSO4).

Correct the recipe of the products based on the charges of the ions.

No need to correct the formula as both compounds currently have their charges balanced.

Refer come the solubility rules table to recognize insoluble commodities which will therefore form a precipitate.

< ceBaCl_2(aq) + Li_2SO_4(aq) ightarrow BaSO_4(s) + LiCl(aq) onumber >

Table 7.5.1 indigenous the previous section reflects that (ceLiCl) is soluble in water, yet (ceBaSO4) is not soluble in water.

Balance the equation:

Although soluble barium salts space toxic, (ceBaSO4) is therefore insoluble that it deserve to be provided to diagnose stomach and also intestinal problems without being absorbed into tissues. An summary of the digestive organs shows up on x-rays of patient who have actually been provided a “barium milkshake” or a “barium enema”—a suspension of very fine (ceBaSO4) particles in water.

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Figure (PageIndex2): an x-ray that the digestive organs that a patience who has swallowed a “barium milkshake.” A barium milkshake is a suspension of very fine BaSO4 particles in water; the high atomic mass that barium renders it opaque come x-rays. (Public Domain; Glitzy queen00via Wikipedia).

Example (PageIndex1)

Predict what will take place if aqueous remedies of rubidium hydroxide and also cobalt(II) chloride room mixed.

Solution

Steps instance

Change the partner of the anions and also cations ~ above the reactant side to kind new compounds (products).

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Correct the recipe of the products based upon the fees of the ions.

(ceRbOH(aq) + CoCl2(aq) ightarrow RbCl+ Co(OH)_2)

Refer come the solubility rules table to identify insoluble commodities which will therefore type a precipitate.

(ceRbOH(aq) + CoCl_2(aq) ightarrow RbCl(aq) + Co(OH)_2(s))
Balance the equation.

Coefficients currently balanced.

(ceRbOH(aq) + CoCl_2(aq) ightarrow RbCl(aq)+ Co(OH)_2(s))


Example (PageIndex2)

Predict what will happen if aqueous services of strontium bromide and also aluminum nitrate are mixed.

Solution

Steps instance

Change the partner of the anions and cations top top the reactant next to form new compound (products).

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Correct the recipe of the products based upon the fees of the ions.

(ceSrBr_2(aq) + Al(NO_3)_3(aq) ightarrow Sr(NO_3)_2 + AlBr_3)

Refer come the solubility rules table to determine insoluble commodities which will therefore kind a precipitate.

(ceSrBr_2(aq) + Al(NO_3)_3(aq) ightarrow Sr(NO_3)_2(aq) + AlBr_3(aq))

According to Table 7.5.1 indigenous the vault section, both (ceAlBr3) (rule 4) and (ceSr(NO3)2) (rule 2) space soluble.

If all possible products space soluble, climate no net reaction will certainly occur.

(ceSrBr_2(aq) + Al(NO_3)_3(aq) ightarrow)

NO REACTION


Exercise (PageIndex2)

Using the details in Table 7.5.1 indigenous the previous section, guess what will take place in each case involving solid electrolytes.

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an aqueous equipment of strontium hydroxide is added to one aqueous solution of iron(II) chloride. Hard potassium phosphate is included to an aqueous systems of mercury(II) perchlorate. Solid sodium fluoride is included to an aqueous systems of ammonium formate. Aqueous solutions of calcium bromide and cesium carbonate room mixed. Answer a Fe(OH)2 precipitate is formed. Answer b Hg3(PO4)2 precipitate is formed. Answer c No Reaction. Answer d CaCO3 is precipitate formed.
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