In each of the following cases, decide whether a precipitate will form when mixing the indicated reagents, and write a balanced equation for the reaction.

1. (a) NaBr(aq) + AgNO₃(aq)
2. (b) KCl(aq) + Pb(NO₃)₂(aq)

Interpretation: Write balanced chemical equation for the given reactions and also predict whether precipitate will form or not.

NaBr(aq)+AgNO3(aq)

Concept introduction: Precipitation reaction takes place when anions and caations present in the solution combine to form insoluble salt. The salt will be soluble or insoluble depends upon the Ksp value of the salt. Higher the Ksp value soluble will be the salt. Salts having lower Ksp value are insoluble or dissolve very less in water.

Generally chlorides, bromides, iodides of Ag+, Pb2+ and Hg22+ are insoluble whereas nitrates are soluble.

Refer to the Appendix J for the value of Ksp.

The Ksp value of AgBr is 5.4×10−13.

Reaction of NaBr with AgNO3 is an example of precipitation and double displacement reaction. Each reactant dissociate to form corresponding ions in the solution and then exchange of ions between two reactant occurs on the basis of their charges either cation or anion to form product.  Therefore the chemical reaction is given as,

  NaBr(aq)+AgNO3(aq)→NaNO3(aq)+AgBr(s)

The number of atoms of each element on both reactant side and product side should be equal for a reaction to be called as balanced chemical reaction.

AgBr formed has very small Ksp value therefore insoluble in water and precipitates out

Interpretation: Write balanced chemical equation for the given reactions and also predict whether precipitate will form or not.

  KCl(aq)+Pb(NO3)2(aq)

Concept introduction: Precipitation reaction takes place when anions and caations present in the solution combine to form insoluble salt. The salt will be soluble or insoluble depends upon the Ksp value of the salt. Higher the Ksp value soluble will be the salt. Salts having lower Ksp value are insoluble or dissolve very less in water.

Generally chlorides, bromides, iodides of Ag+, Pb2+ and Hg22+ are insoluble whereas nitrates are soluble.