Problem 78 - Chemistry: An Atoms-Focused Approach

Question

Zinc hydroxide is amphiprotic. Write chemical equations showing how an aqueous suspension of this compound reacts to the addition of a strong acid and the addition of a strong base.

Step-by-Step Solution

Answer

Answer: The balanced chemical equations are as follows: 1) Reaction with a strong acid (HCl): Zn(OH)2 (s) + 2HCl (aq) → ZnCl2 (aq) + 2H2O (l) 2) Reaction with a strong base (NaOH): Zn(OH)2 (s) + 2NaOH (aq) → Na2Zn(OH)4 (aq)

Step 1: Reaction of Zinc Hydroxide with a Strong Acid (HCl)

Write a balanced chemical equation for the reaction between zinc hydroxide (Zn(OH)2) and hydrochloric acid (HCl). When zinc hydroxide reacts with HCl, it acts as a base and accepts protons, forming zinc chloride (ZnCl2) and water (H2O). The balanced chemical equation is: Zn(OH)2 (s) + 2HCl (aq) → ZnCl2 (aq) + 2H2O (l)

Step 2: Reaction of Zinc Hydroxide with a Strong Base (NaOH)

Write a balanced chemical equation for the reaction between zinc hydroxide (Zn(OH)2) and sodium hydroxide (NaOH). When zinc hydroxide reacts with a strong base like NaOH, it acts as an acid and donates protons, forming the zincate ion (Zn(OH)4^2-) and sodium ions (Na^+). The balanced chemical equation is: Zn(OH)2 (s) + 2NaOH (aq) → Na2Zn(OH)4 (aq) These equations demonstrate the amphiprotic behavior of zinc hydroxide, as it can react with both strong acids and strong bases.

Key Concepts

Understanding Chemical Reactions

Chemical reactions are processes where substances, known as reactants, are transformed into different substances called products. This transformation happens when bonds between atoms are broken and new bonds are formed.

In chemical reactions, the total mass of the products equals the total mass of the reactants, showcasing the principle of "conservation of mass." Every equation representing a chemical reaction must be balanced, meaning the number of atoms of each element must be the same on both sides of the reaction equation.

To understand chemical reactions, consider these key points:

• Reactants: These are the starting materials in a reaction.
• Products: These are the substances formed as a result of the reaction.
• Balanced Equations: These ensure the conservation of mass and must reflect the same number of atoms for each element on both sides of the equation.

Understanding these basics will help you comprehend more complex reactions, such as acid-base interactions.

Exploring Acid-Base Reactions

Acid-base reactions are a special type of chemical reaction characterized by the exchange of protons (H+ ions) between reactants. These reactions are vital in many chemical processes, from industrial applications to biological systems.

When zinc hydroxide, which is amphiprotic, encounters strong acids like HCl, it behaves as a base. It accepts protons, leading to the formation of zinc chloride (ZnCl2) and water. The equation for this reaction is quite simple:

• \[Zn(OH)_2 (s) + 2HCl (aq) \rightarrow ZnCl_2 (aq) + 2H_2O (l)\]

Conversely, when zinc hydroxide reacts with a strong base like NaOH, it behaves as an acid, donating protons. This highlights its amphiprotic nature, as shown in the balanced equation:

• \[Zn(OH)_2 (s) + 2NaOH (aq) \rightarrow Na_2Zn(OH)_4 (aq)\]

These reactions exemplify how substances can act as both acids and bases, depending on the environment they are in.

Understanding Zinc Hydroxide (Zn(OH)2)

Zinc hydroxide is a fascinating compound with the chemical formula Zn(OH)₂. It appears as a white solid and holds an important role in chemistry due to its amphiprotic nature.

Being amphiprotic means zinc hydroxide can act both as an acid and a base. So, it can donate or accept protons depending on the chemical environment.

Here’s a closer look at zinc hydroxide:

• Amphiprotic Behavior: This means it can react with both acids and bases, showcasing its ability to undergo acid-base reactions.
• In Solubility Contexts: Zinc hydroxide tends to be insoluble in water but can dissolve in either strong acids or strong bases, forming different products.

These characteristics make zinc hydroxide an excellent example for studying diverse chemical processes and understanding how compounds can exhibit dual chemical behaviors.