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Introduction to Net Ionic Equation

In chemistry, we depend upon chemical equations to study the behavior of different elements and the mechanism of a chemical reaction. We can write these chemical equations in many ways based on our goals.

For example, if we want to analyze the nature of species reacting in a chemical reaction, we can go with the unbalanced chemical equation. If we want to determine the quantity of the reacting species, then we use a balanced chemical equation. However, if we want to study only the active components of a reaction (the ones which are taking part in the reaction), then we use a net ionic equation.

Related: Read the article to learn about endothermic and exothermic reactions.

We can define the net ionic equation such as

"The chemical equation that displays only those substances participating in a chemical reaction is called a net ionic equation."

Generally, this equation is used to study the chemical reactions which involve strong electrolytes such as neutralization reactions, redox reactions, and double displacement reactions.

Related: Find this article to learn what is synthesis reaction in chemistry.

How to Write Net Ionic Equations?

To write a net ionic equation, you first have to balancing ionic equations and then determine whether the reacting substances form ions or react by giving solid precipitates. It helps to predict the nature of reacting compounds (either ionic or molecular), analyzing strong bases and acids, and predict the solubility ratio of compounds. For this purpose, keep these rules in your mind while writing net ionic equations.

  1. Molecular compounds (sugar, sucrose) don't dissociate into ions when reacting in an aqueous medium.
  2. Ionic compounds always dissociate into ions according to the general rules of solubility while reacting in the aqueous medium.
  3. Weak bases and weak acids partially dissociate, while the strong bases and strong acids dissociate entirely into water.
  4. While writing a net ionic equation, only consider the ions and eliminate all the other species
  5. Break only the strong electrolytes into the corresponding ions
  6. Cancel out the similar ions shown at both sides of the equation with each other.

Related: Also find what is the conversion factor and how these factors affect the rate of reaction.

How to Write a Net Ionic Equation

While writing a net ionic equation, follow these simple steps

  1. First of all, check whether the given equation is balanced or not. If not, then balancing ionic equations using the chemical equation balancer on the home page by using the periodic table. You can also get detailed results with this chemical equation balancer.
  2. Break all the electrolytes into ions and write the complete equation in terms of ions.
  3. While writing the ions of each electrolyte, must mention its formula and charge along with the ionic coefficient (number of each ion to represent its quantity)
  4. After writing the chemical symbol, charge, and ionic coefficient, write aq before each ion to show that the entire process has occurred in an aqueous medium.
  5. All the species which are present either in solid, liquid, or gaseous form will not change.
  6. All the species which would break into ions and possess an aq sign are called spectator ions only if they are present at both sides of the equation. In the end, cancel out the spectator ions or eliminate them simply from the final net equation.

Related: Also find how to determine oxidation number and oxidation state of elements?

Let's write a net ionic equation for a simple reaction to understand the procedure more precisely.

Suppose a reaction between one mole of NaCl in one mole of HCl, the molecular chemical equation of this reaction would be such as

NaCl + HCl - - - > NaCl + H2O

Now break the electrolytes into ions such as

Na+(aq) + Cl-(aq) + H+(aq) + OH-(aq)

Na+(aq) + Cl-(aq) + H2O(l)

As you can see, only the H+ and OH- are participating in the reaction while the Na+ and Cl- keep on floating in the reaction medium from the very first point.

Net Ionic Equation Example

Suppose you have been writing net ionic equations for a reaction between silver nitrate and sodium chloride. First of all, you need to write the balanced chemical equation of this reaction which would be such as

NaCl + AgNO3 - - - > NaNO3 + AgCl

Now, break the electrolytes into ions such as

Na+(aq) + Cl-(aq) + Ag+(aq) + NO-3(aq) - - - > Na+(aq) + NO-3(aq) + AgCl(s)

As you can see, nitrate and sodium are present at both sides of the equation, thus they are spectator ions and not participating in the reaction. Thus, we cancel them out and write the final form of net ionic equation example as follow:

Cl-(aq) + Ag+(aq) - - - > AgCl(s)

Related: How to calculate percent yield step by step.

Bottom Line

Don't forget that we cannot write a net ionic equation for a chemical reaction where all the products are aqueous. In such situations, all the aqueous ions will cancel out with each other, and no ion will be left behind. In other words, for writing net ionic equations for the precipitation reactions, one product precipitates out as solid, liquid, or gas. Moreover, your final net ionic equation should be balanced in terms of both numbers of atoms and charges.

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