# How to write a precipitation reaction equation

Home Writing Complete Ionic Equations When aqueous solutions of sodium phosphate and calcium chloride are mixed together, an insoluble white solid forms. This precipitation reaction is described by the following equation: A molecular equation is one that shows the chemical formulas of all reactants and products but does not expressly indicate their ionic nature. To write the complete ionic equation: The reaction between these two solutes produces an insoluble yellow product. Reactions that result in the formation of an insoluble product are known as precipitation reactions. A precipitate is an insoluble solid formed by a reaction in solution.

Solubility Guidelines for Ionic Compounds The solubility of a substance is the amount of that substance that can be dissolved in a given quantity of solvent. In our discussions any substance with solubility of less than 0. In those cases the attraction between the oppositely charged ions in the solid is too great for the water molecules to separate them to any significant extent, and the substance remains largely undissolved. To predict whether a precipitate will form when solutions are mixed, we must have some knowledge of the solubilities of different compounds.

Unfortunately, there are no rules based on simple physical properties such as ionic charge to guide us. Experimental observations, however, have led to empirical guidelines for ionic compounds. For example, experiments show that all common ionic compounds that contain the nitrate anion, NO3—, are soluble in water.

If you look closely, you will also see an important generalization based on the cation of the compound: Our plan is to use Table 4. Thus, we need to focus on the anion in each compound because the table is organized by anion.

Thus, Na2CO3 is soluble in water.

## HOMEWORK SOLVED

Thus, PbSO4 is insoluble in water. Refer to Table 4. Notice also that OH— compounds, while usually insoluble, nevertheless form soluble compounds with alkali metal cations; thus, NaOH is also water soluble. Will either of the cations interact with either of the anions to form an insoluble compound?

The balanced equation for the precipitation reaction is [4. It is only after the chemical formulas of the products are determined that the equation can be balanced.

Reactions in which positive ions and negative ions appear to exchange partners conform to the following general equation: Such reactions are known as exchange reactions or metathesis reactions meh-TATH-eh-sis, which is the Greek word for "to transpose".

Precipitation reactions conform to this pattern, as do many acid-base reactions, as we will see in Section 4. Our strategy is to consider the ions present in the reactants and to exchange the anions between the two cations.

## Precipitation Reactions

Once we have written the chemical formulas for these products, we can use Table 4. Thus, BaSO4 is insoluble and will precipitate from solution. In contrast, Table 4. An equation written in this fashion, showing the complete chemical formulas of the reactants and products, is called a molecular equation, because it shows the chemical formulas of the reactants and products without indicating their ionic character.

Because Pb NO3 2, KI, and KNO3 are all soluble ionic compounds, we can write the chemical equation to indicate explicitly the ions that are in the solution: Ions that appear in identical forms among both the reactants and products of a complete ionic equation are called spectator ions.

They are present but play no direct role in the reaction. When spectator ions are omitted from the equation they cancel out like algebraic quantitieswe are left with the net ionic equation.

Charge is conserved in reactions, so the sum of the charges of the ions must be the same on both sides of a balanced net ionic equation. If everything in a complete ionic equation is a spectator, it means that no reaction occurs.

Net ionic equations are widely used to illustrate the similarities between large numbers of reactions involving electrolytes. For example, Equation 4.

Thus, a net ionic equation helps us appreciate that more than one set of reactants can lead to the same net reaction. The complete equation, in contrast, identifies the actual reactants that participate in a reaction.

Net ionic equations remind us of another important fact:precipitation reaction, and the solid produced in the reaction is known as the precipitate. You can predict whether You can predict whether a precipitate will form using a list of solubility rules such as those found in the table below.

Chemistry or Mathematics? Finding coefficients for chemical reactions is often complicated, especially in the case of redox processes.

The classical approach uses oxidation numbers and many chemists cannot imagine any way to find the solution other than balancing half-reactions for the process. Be sure the equation is balanced.

Step II. Write the complete ionic equation. Separate soluble substances into ions. Leave insoluble substances alone. Be sure the equation is still balanced, both in atoms and charges. Step III. Write the net ionic equation by eliminating the spectator ions if necessary, reduced the coefficients to their lowest values (whole number).

## Basic chemistry help for students and teachers

Write a molecular equation for the precipitation reaction that occurs? Chemistry 6 years ago _biology ilikescience 1 Reply Views Write the net ionic equation for any precipitation reaction that may be predicted by the solubility rules on t?

Equation Writing for Precipitation Reactions. Example - aqueous copper(II) nitrate and aqueous sodium phosphate are mixed. Writing the molecular equation. attheheels.com the reaction in words exchanging anions and cations of the reactants to form the.

products. A precipitation reaction is a . A net ionic equation shows us the ions that are actually participating in the reaction (versus the remaining ions that do not participate, called spectator ions).

In your case the zinc and hydroxide ions were the only ions participating, as they were the only ions that formed a new substance; a precipitate.

Aqueous Reactions