Question

Is a saline ( \(\mathrm{NaCl}\) ) solution at \(80^{\circ} \mathrm{C}\) acidic, basic, or neutral?

Short answer

A saline solution (NaCl) at 80°C is neutral. This is because the ions produced when NaCl dissolves in water do not alter the acidity or basicity of the solution. Additionally, the increased temperature does not affect the pH of the solution since the ionization of water at higher temperatures affects both acidic and basic ions equally, maintaining the pH of the solution at a neutral value.

Step-by-step solution

Understand the properties of NaCl

Sodium chloride (NaCl) is a salt formed from the neutralization reaction between a strong acid (hydrochloric acid, HCl) and a strong base (sodium hydroxide, NaOH). When NaCl is dissolved in water, it dissociates into its constituent ions, Na\(^+\) and Cl\(^-\).

Observe the behavior of Na\(^+\) and Cl\(^-\) ions in water

When NaCl dissociates in water, the Na\(^+\) and Cl\(^-\) ions interact with water molecules. However, since both ions come from strong acid (HCl) and strong base (NaOH), they do not react with water to form either hydronium (H\(_3\)O\(^+\)) ions or hydroxide (OH\(^-\)) ions. This means that they do not alter the acidity or basicity of the solution.

Consider the effect of temperature

In this scenario, the saline solution is at \(80^{\circ} \mathrm{C}\). The effect of temperature on the ionization of water should be considered. At higher temperatures, the ionization of water increases, which results in an increase in the concentration of both H\(_3\)O\(^+\) and OH\(^-\) ions in the solution. However, since the concentration of both ions increases equally, the overall pH of the solution remains neutral (pH = 7).

Conclusion

A saline solution (NaCl) at \(80^{\circ} \mathrm{C}\) is neutral, as the ions produced when NaCl dissolves in water do not alter the acidity or basicity of the solution. The increased temperature doesn't affect the conclusion since the increase in ionization of water at higher temperatures affects both acidic and basic ions equally, maintaining the pH of the solution at a neutral value.

Key concepts

Ionization

Ionization is the process by which a molecule splits into ions when dissolved in a solvent, such as water. Sodium chloride (NaCl) ionizes into sodium (Na\(^+\)) and chloride (Cl\(^-\)) ions when dissolved. This is because NaCl is an ionic compound, and in water, the ionic bonds break.
This results in the dissociation of NaCl into its constituent ions. However, it's essential to understand that ionization doesn't mean changing the acidity or basicity of a solution.
For NaCl, the ionization is simply a physical process where Na\(^+\) and Cl\(^-\) ions remain stable and do not undergo further reaction with water molecules to affect pH.

Neutralization

Neutralization is a chemical reaction between an acid and a base to form a salt and water. In the case of sodium chloride, it is formed from the neutralization of hydrochloric acid (HCl) and sodium hydroxide (NaOH).
Both are strong acids and bases, meaning they completely dissociate in water to form ions.
This complete dissociation results in the formation of a neutral salt solution when mixed.

• Hydrochloric Acid (HCl) provides hydrogen ions (H\(^+\)).
• Sodium Hydroxide (NaOH) provides hydroxide ions (OH\(^-\)).
• These ions combine to form water, leaving salt in the solution.

Because the resultant salt, NaCl, doesn't interact with water to form additional H\(^+\) or OH\(^-\), the solution remains neutral.

Sodium Chloride

Sodium chloride (NaCl), commonly known as table salt, is an essential compound used widely in cooking and preservation. It is a crystalline solid that readily dissolves in water.
When NaCl is added to water, it separates into Na\(^+\) and Cl\(^-\) ions, yet, unlike some salts, NaCl remains inactive in terms of altering the solution's pH.
This unique property of NaCl comes from its formation during a neutralization process where a strong acid and a strong base interact.

• Forms through neutralization, balancing acid and base properties.
• Dissolves but does not alter solution acidity or basicity.
• Widely used due to its stable and inert nature in solutions.

pH

The pH scale measures how acidic or basic a solution is, ranging from 0 to 14. A pH of 7 indicates a neutral solution, like pure water. Sodium chloride solutions typically stay at this neutral pH.
NaCl doesn't produce H\(^+\) or OH\(^-\) ions upon dissolving, so it doesn't affect pH levels.
The neutrality of a solution is maintained as long as no excess acidic or basic ions are present. In water, any increase in ion concentration due to temperature changes affects both H\(^+\) and OH\(^-\) equally, keeping the solution neutral.

• Neutral pH around 7 for NaCl solutions.
• Stable in varying conditions unless additional ions are introduced.

Temperature Effect

Temperature can influence a solution's characteristics, such as its solubility and reaction rate. For a saline solution, a rise in temperature affects water's ionization,
yet despite these changes, the overall pH often remains neutral.
As temperature increases, water tends to ionize more, raising both H\(^+\) and OH\(^-\) concentrations. Importantly, these changes occur symmetrically, leaving the pH stable.

• Higher temperatures increase water ionization, but balanced.
• NaCl remains neutral in its influence despite temperature effects.
• Ensures the solution doesn't stray from its neutral pH.

Understanding temperature's effect assists in grasping why a saline solution at 80°C remains neutral.