Problem 61 - Chemistry and Chemical Reactivity

Question

When an electric current is passed through an aqueous solution of NaCl, the valuable industrial chemicals \(\mathrm{H}_{2}(\mathrm{g}), \mathrm{Cl}_{2}(\mathrm{g}),\) and \(\mathrm{NaOH}\) are produced. \(2 \mathrm{NaCl}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(\ell) \rightarrow\) $$ \mathrm{H}_{2}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g})+2 \mathrm{NaOH}(\mathrm{aq}) $$

Step-by-Step Solution

Answer

An electric current electrolyzes NaCl solution, producing \( \text{H}_2 \), \( \text{Cl}_2 \), and \( \text{NaOH} \).

Step 1: Analyze the Reaction Equation

The given chemical equation is \( 2 \text{NaCl} (\text{aq}) + 2 \text{H}_2\text{O} (\ell) \rightarrow \text{H}_2 (\text{g}) + \text{Cl}_2 (\text{g}) + 2 \text{NaOH} (\text{aq}) \). This is a balanced chemical equation showing the reactants and products in an aqueous solution.

Step 2: Identify the Reactants

The reactants in this process are \( 2 \text{NaCl} (\text{aq}) \) and \( 2 \text{H}_2\text{O} (\ell) \), which implies that the process involves sodium chloride dissolved in water.

Step 3: Identify the Products

The products of this electrochemical reaction are \( \text{H}_2 (\text{g}) \), \( \text{Cl}_2 (\text{g}) \), and \( 2 \text{NaOH} (\text{aq}) \). These are valuable industrial chemicals.

Step 4: Understand the Reaction Type

This is an electrolysis reaction where an electric current is used to drive a non-spontaneous chemical reaction. Sodium chloride in water undergoes electrolysis to produce hydrogen gas, chlorine gas, and sodium hydroxide.

Step 5: Conservation of Mass Check

Ensure that the number of each type of atom is the same on both sides of the reaction equation. We have 2 Na, 2 Cl, 4 H, and 2 O on both sides of the equation, confirming it's balanced.

Key Concepts

Chemical Reactions

A chemical reaction is a process where reactants are transformed into products. During this process, bonds between atoms are broken and new bonds form, creating different substances. In the reaction involving sodium chloride (\(\text{NaCl}\)) and water (\(\text{H}_2 ext{O}\)), these substances are subjected to an electric current. This prompts the reactants to rearrange and form new products: hydrogen gas (\(\text{H}_2( ext{g})\)), chlorine gas (\(\text{Cl}_2( ext{g})\)), and sodium hydroxide (\(\text{NaOH}\)).
- Chemical reactions include various types: synthesis, decomposition, single displacement, double displacement, and combustion.- Electrolysis, as seen in this process, is a type of decomposition reaction driven by electricity.
Understanding chemical reactions is essential because they form the basis of chemical processes and transformations. They are present in numerous everyday and industrial processes, affecting everything from cooking to complex industrial manufacturing.

Industrial Chemistry

Industrial chemistry is the branch of chemistry that focuses on manufacturing chemicals on a large scale for commercial purposes. The electrolysis of sodium chloride (\(\text{NaCl}\)) solution is a classic example. This process not only produces valuable chemicals but also supports various industries.- Sodium hydroxide (\(\text{NaOH}\)), commonly known as lye, is crucial in the production of soap, paper, and textiles.- Chlorine (\(\text{Cl}_2\)) is extensively used in disinfecting water and making plastics like PVC.- Hydrogen gas (\(\text{H}_2\)) serves as a clean energy source and is used in refining industries.
By optimizing reactions such as the electrolysis of \(\text{NaCl}\), industrial chemists help enhance efficiency and sustainability in chemical production. This not only boosts economic growth but also ensures environmental protection.

Balancing Chemical Equations

Balancing chemical equations is crucial to maintaining the law of conservation of mass. This law states that mass is neither created nor destroyed in a chemical reaction. Therefore, the number of atoms of each element must be the same on both sides of the equation.\[2 \text{NaCl} (\text{aq}) + 2 \text{H}_2\text{O} (\ell) \rightarrow \text{H}_2 (\text{g}) + \text{Cl}_2 (\text{g}) + 2 \text{NaOH} (\text{aq}) \]- This balanced equation shows that there are 2 sodium (\(\text{Na}\)), 2 chlorine (\(\text{Cl}\)), 4 hydrogen (\(\text{H}\)), and 2 oxygen (\(\text{O}\)) atoms on each side.- Balancing not only ensures the correctness of chemical representation but also helps in calculating the amounts of reactants and products accurately.
Practicing balancing is fundamental for students, as it underpins much of the work done in both academic and laboratory settings, effectively communicating the precise details of chemical reactions.

Electrochemistry

Electrochemistry explores the relationship between electrical energy and chemical reactions. Electrolysis is a process that uses electric current to drive non-spontaneous chemical reactions, such as splitting sodium chloride in water to produce \(\text{H}_2\), \(\text{Cl}_2\), and \(\text{NaOH}\).- In electrolysis, an electric current causes ions to move to the electrodes: positive ions to the cathode (where reduction occurs) and negative ions to the anode (where oxidation occurs).- This movement and transformation are harnessed to produce compounds that would not typically form under normal conditions without external energy.
Understanding electrochemistry is foundational for various fields, including battery technology, corrosion study, and metallurgy. It improves our ability to innovate and develop new energy solutions, showcasing the versatility and importance of this area of chemistry in modern technology and industry.