Problem 74 - Introductory Chemistry Atoms First

Question

Write the intact-molecule equation and the net ionic equation for the neutralization reaction between perchloric acid, \(\mathrm{HClO}_{4}(a q)\), and \(\mathrm{NaOH}(a q)\). What salt is in solution once the reaction is run?

Step-by-Step Solution

Answer

The intact-molecule equation for the neutralization reaction between perchloric acid, $\mathrm{HClO}_{4}(a q)$, and $\mathrm{NaOH}(a q)$ is: \[\mathrm{HClO}_4(aq) + \mathrm{NaOH}(aq) \rightarrow \mathrm{NaClO}_4(aq) + \mathrm{H}_2\mathrm{O}(l)\] The net ionic equation is: \[\mathrm{H}^+(aq) + \mathrm{OH}^-(aq) \rightarrow \mathrm{H}_2\mathrm{O}(l)\] The salt in solution once the reaction is run is sodium perchlorate, $\mathrm{NaClO}_4$.

Step 1: 1. Write the chemical equation for the reaction with intact molecules

First, we need to write the chemical reaction between perchloric acid, HClO4, and sodium hydroxide, NaOH. We know that acids and bases react with each other to form water and a salt. Therefore, the intact-molecule equation will be: HClO4(aq) + NaOH(aq) -> NaClO4(aq) + H2O(l)

Step 2: 2. Write the complete ionic equation

Next, we need to write the complete ionic equation by dissociating the soluble ionic compounds into their individual ions: H+(aq) + ClO4^-(aq) + Na+(aq) + OH^-(aq) -> Na+(aq) + ClO4^-(aq) + H2O(l)

Step 3: 3. Write the net ionic equation

Now, we can write the net ionic equation by eliminating spectator ions (ions that appear on both sides of the equation). In this case, the spectator ions are Na+(aq) and ClO4^-(aq). Thus, the net ionic equation will be: H+(aq) + OH^-(aq) -> H2O(l)

Step 4: 4. Identify the salt formed in the solution

The salt formed in the solution after the reaction between perchloric acid and sodium hydroxide is sodium perchlorate (NaClO4). In conclusion, the intact-molecule equation is: HClO4(aq) + NaOH(aq) -> NaClO4(aq) + H2O(l) The net ionic equation is: H+(aq) + OH^-(aq) -> H2O(l) And the salt formed in the solution once the reaction is run is sodium perchlorate (NaClO4).

Key Concepts

Intact-Molecule Equation

In a chemical reaction, the intact-molecule equation is a straightforward representation of the reactants and products written in their complete molecular form. In the case of the neutralization reaction between perchloric acid and sodium hydroxide, the intact-molecule equation does not show the ionic dissociation but gives a quick overview of the chemical process.

This particular reaction can be written as:

• ext{HClO}_4( ext{aq}) + ext{NaOH}( ext{aq}) ightarrow ext{NaClO}_4( ext{aq}) + ext{H}_2 ext{O}( ext{l})

Here, we see the strong acid, ext{HClO}_4, reacting with the strong base, ext{NaOH}, to form water ( ext{H}_2 ext{O}) and the salt, sodium perchlorate ( ext{NaClO}_4).

Remember, the intact-molecule equation is ideal for getting a complete picture of the substances involved in the reaction, even if it does not depict the ionic details.

Net Ionic Equation

The net ionic equation is a streamlined version of a chemical equation that only displays the species that undergo change during the reaction. This is particularly useful for identifying the essence of the reaction, such as which ions are actually involved in the transformation.

In our neutralization reaction between ext{HClO}_4 and ext{NaOH}, the reaction can be simplified to:

• ext{H}^{+}( ext{aq}) + ext{OH}^{-}( ext{aq}) ightarrow ext{H}_2 ext{O}( ext{l})

By focusing only on the reaction between the hydrogen ions ( ext{H}^{+}) and the hydroxide ions ( ext{OH}^{-}), we can see that the essential outcome is the production of water. This simplification helps us understand that the core of the neutralization process is the formation of water from these ions.

The net ionic equation eliminates spectators, making it perfect for understanding the fundamental chemistry at play.

Spectator Ions

Spectator ions are those ions present in the solution that do not participate directly in the chemical reaction. They remain unchanged on both sides of a chemical equation. Recognizing spectator ions is crucial in writing net ionic equations because they can be omitted to simplify the equation.

In the neutralization reaction we're examining, the spectator ions are ext{Na}^{+}(aq) and ext{ClO}_4^{-}(aq). Though these ions are present in the reaction mixture,

• They do not undergo a change in oxidation state.
• They appear as reactants and products without alteration.

As such, these ions are ignored in the net ionic equation, which focuses only on the ions that participate in the formation of water.

Acid-Base Reaction

An acid-base reaction is a fundamental chemical reaction where an acid reacts with a base to produce salt and water. This is one of the main types of double displacement reactions where the hydrogen ion from the acid reacts with the hydroxide ion from the base.

The acid-base reaction in our exercise involves perchloric acid ( ext{HClO}_4), a strong acid, and sodium hydroxide ( ext{NaOH}), a strong base. The general formula for neutralization reactions is:

• ext{Acid} + ext{Base} ightarrow ext{Salt} + ext{Water}

The main takeaway is that these reactions result in the formation of water and a neutral salt, such as sodium perchlorate ( ext{NaClO}_4) in this case. Understanding these reactions is crucial because they represent a key concept in chemistry, illustrating the interaction between ions, the conservation of mass, and the transfer of energy.