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As you know, one of three products (form a solid, water or gas) must be produced in a double chemical reaction for the reaction to occur. Here, we will explain formation of one of these products: the formation of water.
As with all double replacement reactions, you have two reactants that are aqueous (compounds that break-up into their ions in water). In other words, you have a bucket of ions before the reaction occurs. The task is to rearrange the ions into new compounds (cpds) knowing that like charged ions can't create cpds.
Even though water (H2O) is a molecular cpd, we often think of it as made up of two ions, hydronium ion (H+1) and hydroxide ion (OH-1). It would look like HOH if written as a cpd. Therefore, one of our reactants must contain the hydroxide ion (OH-1) and one must contain the hydronium ion (H+1). If you place these two reactants into a bucket, you product water (H2O). See example below.
These types of reactions are very common place to the point that we give the reactants and chemical reaction special names:
- Acid - a compound that breaks up into ions in water where one of the ions is hydronium ion (H+1). Acids look like ionic cpd that has H as the cation. Example#1, HNO3 breaks up into 1 H+1 and 1 NO3-1. Example#2, H2SO4 breaks up into 2 H+1 and 1 SO4-2.
- Base - a compound that breaks up into ions in water where one of the ions is the hydroxide ion (OH-1).
- Neutralization Rxn - a double replacement reaction that produces water (H2O) as one of its products. The two reactants are an acid & a base.
- Examples of Neutralization Reaction
- 1 NaOH(aq) + 1 HCl(aq) ==> 1 H2O(l) (or 1 HOH(l)) + NaCl(aq)
- 1 Ca(OH)2 (aq) + 2 HCl(aq) ==> 2 H2O(l) (or 2 HOH(l)) + CaCl2 (aq)
Net Ionic Reaction for Neutralization Reactions
To determine any Net Ionic Reaction, you must follow the directions stated in (NetIonicReactions).
- Example of Determining Net Ionic Reactions for Neutralization Reaction
- Step 1: 1 Ca(OH)2 (aq) + 2 HCl(aq) ==> 2 H2O(l) + CaCl2 (aq) (Balanced Molecular Equation)
- Step2 : 1 Ca+2 + 2 OH+1 + 2 H+1 + 2 Cl-1 --> 2 H2O(l) + 1 Ca+2 + 2 Cl-1
- Step 3: I can't show on this webpage cancel out of spectator ions. You can do it right on work above. The spectator ions are Ca+2 and 2 Cl-1 since they are the same on both side of arrow.
- Step 4: 2 OH-1 + 2 H+1 --> 2 H2O(l)
- But you can cancel out a "2" in each of the coefficient so the actual Net Ionic Reaction is
- 1 OH-1 + 1 H+1 --> 1 H2O(l)
(The Special Condition for Net Ionic Reactions of Neutralization is that all neutralization reactions have the same Net Ionic Reaction: the one above)