Video Transcript
What is the net ionic equation for
the neutralization between ammonium hydroxide and hydrochloric acid? NH4OH aqueous plus HCl aqueous
reacts to form NH4Cl aqueous plus H2O liquid. (A) H+ aqueous plus OH− aqueous
reacts to form H2O liquid. (B) NH4+ aqueous plus H+ aqueous
plus OH− aqueous reacts to form NH4+ aqueous plus H2O liquid. (C) NH4+ aqueous plus OH− aqueous
reacts to form NH3+ aqueous plus H2O liquid. (D) NH4+ aqueous plus Cl− aqueous
reacts to form NH4Cl aqueous. (E) H+ aqueous plus H2O liquid
reacts to form H3O+ aqueous.
The net ionic equation for a
reaction is a way of expressing the chemical equation with all of the spectator ions
removed. Spectator ions are ions that are
involved in a reaction that don’t actually participate in the chemical change. To identify them, we’re first going
to need to break apart all of these aqueous reactants and products into the ions
that make them up, since when an ionic species is aqueous, it’s broken up into the
ions that it’s made of. I’ll remove the answer choices so
that we have room to write everything out.
Our first chemical species,
ammonium hydroxide, is aqueous. It will break apart into NH4 or
ammonium ions and OH− or hydroxide ions when it’s in solution. Our next reactant is hydrochloric
acid. Since it’s aqueous, it will break
apart into hydrogen ions and chloride ions when it’s dissolved in water. Now let’s move on to the product
side of the reaction. Our first product, ammonium
chloride, is also aqueous, so it will be split up into NH4 ions and Cl− ions. Our final product is water. Since water is a liquid, it doesn’t
break up into ions, so we’ll leave it alone. This equation that we’ve ended up
with is called the ionic equation, since it shows all of the chemical species that
are involved in the reaction as broken up into the ions that make them up.
Now that we have our ionic
equation, we can identify the spectator ions in this reaction. Since spectator ions don’t
participate in the chemical change, they’ll appear on both the reactant side and the
product side of the reaction. Looking through our reactants and
products, we can see that ammonium appears on both the reactant side and the product
side, as does the chloride ion. So if we remove these spectator
ions, we’ll end up with a net ionic equation for this reaction. On the reactant side, removing the
spectator ions just leaves us with OH− and H+ ions. And on the product side, all we’re
left with is water. So this is the net ionic equation
for the reaction. OH− aqueous plus H+ aqueous reacts
to form H2O liquid. So now if we bring back our answer
choices, we can see that the net ionic equation that we came up with matches answer
choice (A).
