Video Transcript
What is the balanced net ionic
equation for the reaction between an ammonium ion and sodium hydroxide?
The presence of ammonium ions can
be tested using sodium hydroxide. For example, a dilute sodium
hydroxide solution can be added to an unknown solution and the results observed. If the solution contains ammonium
ions, a few small bubbles will form. The solution may need to be heated
slightly to initiate the reaction. A gas is produced if ammonium ions
are present. The gas that is being released is
ammonia gas, which has the chemical formula NH3.
If enough ammonia gas is formed, we
may be able to detect it by its pungent odor. However, ammonia, like many other
gases in the laboratory, is toxic in large quantities, so smelling a gas to detect
it is not advisable. A safer way to test for the
presence of ammonia gas is to hold a piece of moist red litmus paper near the mouth
of the test tube. If the litmus paper turns blue,
then we know that the ammonia gas is forming an alkali on the paper.
If we know that the reaction
between ammonium ions and hydroxide ions forms ammonia gas, we can begin to write a
balanced net ionic equation. We can deduce that the second
product of this reaction will be water. The net ionic equation looks like
this. A net ionic equation is a
simplified ionic equation that only shows the species involved in the chemical
reaction. Any other ions present in the
solution would be spectator ions and are not necessary to write in a net ionic
equation.
The ionic equation for this
reaction is shown. In this case, the sodium cations
from sodium hydroxide are not active participants in the reaction and are thus
spectator ions. Therefore, the balanced net ionic
equation for the reaction between an ammonium ion and sodium hydroxide is NH4+
aqueous reacts with OH− aqueous to form NH3 gas and H2O liquid.
