Question

Could a buffered solution be made by mixing aqueous solutions of HCl and NaOH? Explain.

Short answer

No, a buffered solution cannot be made by mixing HCl and NaOH solutions. When these solutions are mixed, a neutralization reaction occurs, producing water and the neutral salt NaCl. HCl and NaOH are both strong acids and bases, respectively, and do not have significant conjugate species to create a buffering effect. Moreover, NaCl does not affect the pH of the solution, so the resulting solution will not be buffered and cannot maintain its pH when small amounts of acids or bases are added.

Step-by-step solution

Understanding the components

HCl is a strong acid that dissociates completely in water, producing H+ ions and Cl- ions. On the other hand, NaOH is a strong base that also dissociates completely in water, producing Na+ ions and OH- ions. When we mix these two solutions, a neutralization reaction occurs, producing water and a salt, NaCl.

Considering the neutralization reaction

The neutralization reaction that occurs when HCl and NaOH are mixed can be represented by the following equation: HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq) This reaction goes to completion as both HCl and NaOH are strong acids and bases, respectively, and no significant amount of the reactants will be left in the solution.

Evaluating the possibility of a buffered solution

A buffered solution is typically created by mixing a weak acid and its conjugate base, or a weak base and its conjugate acid, in roughly equal amounts. This allows the buffering action to occur as the weak acid or base can react with added H+ or OH- ions without significantly shifting the pH of the solution. In the case of mixing HCl and NaOH solutions, we form NaCl as the final product. Since HCl and NaOH are strong acid and base, they don't have a significant conjugate species to create a buffering effect. Moreover, NaCl is a neutral salt which will not affect the pH of the solution. Therefore, this resulting solution will not be buffered, as it cannot maintain its pH when small amounts of acids or bases are added.

Conclusion

Mixing aqueous solutions of HCl and NaOH will result in a neutralization reaction that produces water and NaCl, which is a neutral salt with no buffering capacities. Therefore, a buffered solution cannot be created by mixing HCl and NaOH solutions.

Key concepts

Neutralization Reaction

When you mix an acid and a base together, a neutralization reaction occurs. This is a fascinating process in chemistry where an acid and a base react to form water and a salt. - For example, when hydrochloric acid (HCl) is mixed with sodium hydroxide (NaOH), they produce water (H\(_2\)O) and sodium chloride (NaCl).- The reaction can be written as: \[ \text{HCl}(aq) + \text{NaOH}(aq) \rightarrow \text{H}_2\text{O}(l) + \text{NaCl}(aq) \]Neutralization reactions typically result in a pH that is more neutral than the original acid or base. In this specific reaction between HCl and NaOH, both being strong reaction components, they completely neutralize each other. The products are neutral, consisting mainly of water and a salt that does not contribute to the acidity or basicity of the solution.

Strong Acid and Base

Strong acids and bases, like HCl and NaOH, dissociate completely in water. They release high concentrations of ions, which accounts for their strong reactions.- **Strong Acid:** HCl dissociates completely into H\(^+\) (hydrogen ions) and Cl\(^-\) (chloride ions).- **Strong Base:** NaOH dissociates completely into Na\(^+\) (sodium ions) and OH\(^-\) (hydroxide ions).This complete dissociation means they can swiftly neutralize each other, as seen in the reaction: \[ \text{H}^+(aq) + \text{OH}^-(aq) \rightarrow \text{H}_2\text{O}(l) \]The thorough neutralization leads to no leftover H\(^+\) or OH\(^-\) ions. Hence, after reacting, the solution becomes neutral with no additional acidic or basic effect from the original reactants. This is what makes strong acids and bases different from weak ones, as weak ones do not dissociate entirely.

pH Balance

pH is a measure of how acidic or basic a solution is, on a scale of 0 to 14. Neutral solutions have a pH of 7. - **Acidic solutions** have a pH less than 7, while **basic solutions** have a pH greater than 7. - Neutralization reactions aim to bring the pH closer to 7, creating a balanced environment. When HCl (acid) and NaOH (base) react, they form water and NaCl, which does not alter the pH. The result is a neutral solution with a pH of around 7. In buffer systems, this balancing is crucial for maintaining a stable pH against minor additions of acid or base. However, due to the complete reaction of strong acids and bases like HCl and NaOH, they can't form a buffer system. Instead, they stabilize each other completely into neutral results, extreme compared to buffer compounds, which moderate changes efficiently.

Conjugate Base and Acid

In chemistry, conjugate acids and bases play a vital role in buffer solutions. These are the species that remain after an acid has donated a proton or a base has accepted a proton. - **Conjugate Acid-Base Pair:** Formed when a weak acid and its conjugate base, or a weak base and its conjugate acid, are in equilibrium. These couples are what provide the buffering ability by reacting with either additional acids or bases added to the solution. Why Not HCl and NaOH? - **Lack of Conjugate Species:** Strong acids like HCl and strong bases like NaOH dissociate entirely, leaving no effective conjugate pair to control pH fluctuations. - **Neutral Products:** After neutralization, NaCl and water are formed, neither of which has basic or acidic properties capable of occurring in conjugate systems. Understanding conjugates is crucial for knowing how buffer solutions work. Strong acids and bases lack the necessary properties to create a functional buffered solution. This makes them unsuitable when the goal is to establish a solution capable of resisting pH changes.