Chapter 9, Problem 78A

Interpretation Introduction

Interpretation:

The conditions when a precipitate form in a chemical reaction needs to be explained.

Concept introduction:

In a chemical reaction, the reactants are written on the left side of the equation and the product is written on the right side. The product and the reactants contain an arrow between them showing the proceeding of the reaction from the reactants to the products.

Answer to Problem 78A

The precipitate occurs in a reaction when ionic products exceeds the solubility product of the compound.

Explanation of Solution

When aqueous solution of some ionic solutes combine, precipitate of generally one product is generated. This is a type of double displacement reaction. The precipitate occurs in such reaction when ionic products exceeds the solubility product of the compound. Under this condition, precipitate is generated.

As an example of precipitation reaction, one can take the reaction between sodium hydroxide and copper chloride.

$\text{2NaOH+}{\text{CuCl}}_{\text{2}}\left(\text{aq}\right)\to \text{2NaCl}\left(\text{aq}\right)\text{+}\text{Cu}{\left(\text{OH}\right)}_{\text{2}}\left(\text{s}\right)$

In this reaction $\text{Cu}{\left(\text{OH}\right)}_{\text{2}}\left(\text{s}\right)$ is the precipitate generated.

Conclusion

When aqueous solution of some ionic solutes combine, precipitate of generally one product is generated. This is a type of double displacement reaction.