In the following reactions, ZnO is respectively acting as a/an
(i) ZnO + Na2O - Na2ZnO2
(ii) ZnO +

Q: How do I quickly determine if an oxide is acidic or basic?

As a general rule of thumb, metallic oxides (like $\text{Na}_2\text{O}$, $\text{CaO}$) are basic, while non-metallic oxides (like $\text{CO}_2$, $\text{SO}_3$) are acidic.

Q: What exactly is an amphoteric oxide?

An amphoteric oxide is a unique substance that can behave as both an acid and a base. It reacts with acids to form salt and water, and it also reacts with bases to form salt and water.

Q: Are there other amphoteric oxides I should memorize?

Absolutely! Besides $\text{ZnO}$, you should definitely remember $\text{Al}_2\text{O}_3$, $\text{PbO}$, $\text{SnO}$, and $\text{BeO}$. They are frequent stars in JEE chemistry!

Q: Why does $\text{ZnO}$ act as an acid with $\text{Na}_2\text{O}$?

$\text{Na}_2\text{O}$ is a very strong base. When placed in an environment with a strong base, the amphoteric $\text{ZnO}$ is forced to exhibit its acidic properties to undergo a neutralization reaction.

Q: What is the name of the salt $\text{Na}_2\text{ZnO}_2$?

It is called sodium zincate. It's a classic complex salt formed when zinc or zinc oxide dissolves in a strong alkali like sodium hydroxide.

Question

In the following reactions, $	ext{ZnO}$ is respectively acting as a/an
(i) $	ext{ZnO} + 	ext{Na}_2	ext{O} \longrightarrow 	ext{Na}_2	ext{ZnO}_2$
(ii) $	ext{ZnO} + 	ext{CO}_2 \longrightarrow 	ext{ZnCO}_3$

Options:

(A) base and acid

(B) base and base

(C) acid and acid

(D) acid and base

Sigma Percentile · Accepted Answer

### The Dual Personality of Zinc Oxide

In the fascinating world of inorganic chemistry, most oxides pick a side. They are either acidic or basic. However, a select few possess a unique dual personality, allowing them to act as both. We call these chemical chameleons **amphoteric oxides**. Zinc oxide ($	ext{ZnO}$) is one of the most famous examples of this phenomenon.

To understand how $	ext{ZnO}$ behaves in a given reaction, we must play the role of a chemical detective and investigate the nature of the compound it is reacting with. The fundamental rule of neutralization states that an acid reacts with a base to form a salt. Let's apply this logic to the two reactions provided in the problem.

### Analyzing the First Reaction

In the first scenario, zinc oxide is paired with sodium oxide:

$$ 	ext{ZnO} + 	ext{Na}_2	ext{O} \longrightarrow 	ext{Na}_2	ext{ZnO}_2 $$

Our first step is to identify the nature of $	ext{Na}_2	ext{O}$. Sodium is a highly electropositive alkali metal. As a general rule, **oxides of active metals are strongly basic**. Because $	ext{Na}_2	ext{O}$ is a strong base, it forces the amphoteric $	ext{ZnO}$ to exhibit its acidic properties.

In this neutralization process, $	ext{ZnO}$ acts as an **acid**, reacting with the basic $	ext{Na}_2	ext{O}$ to form the salt sodium zincate ($	ext{Na}_2	ext{ZnO}_2$).

### Analyzing the Second Reaction

Now, let's shift our focus to the second reaction, where zinc oxide encounters carbon dioxide:

$$ 	ext{ZnO} + 	ext{CO}_2 \longrightarrow 	ext{ZnCO}_3 $$

Here, the partner is $	ext{CO}_2$. Carbon is a non-metal, and **non-metallic oxides are generally acidic** in nature (think about how $	ext{CO}_2$ dissolves in water to form carbonic acid).

Faced with an acidic environment, the versatile $	ext{ZnO}$ flips its behavior. It now acts as a **base** to neutralize the acidic $	ext{CO}_2$, resulting in the formation of the salt zinc carbonate ($	ext{ZnCO}_3$).

### The Final Verdict

By carefully analyzing the reacting partners, we have successfully unmasked the role of zinc oxide in both scenarios. In the first reaction with a strong base, it acts as an **acid**. In the second reaction with an acidic oxide, it acts as a **base**.

This perfectly aligns with option (d), beautifully demonstrating the concept of amphoterism. Always remember to look at the company a compound keeps to understand its chemical behavior!

Animated Solution for Chemistry - d and f-Block Elements: In the following reactions, $ZnO$ is respectively acting as a/an (i) $ZnO + Na_{2} O ⟶ Na_{2} ZnO_{2}$ (ii) $ZnO + CO_{2} ⟶ ZnCO_{3}$

Select Answer:

Visualized Solution

\text{Analyzing the Reactants}

\text{Nature of } \text{Na}_2\text{O}

\text{Role of } \text{ZnO} \text{ in Reaction 1}

\text{Nature of } \text{CO}_2

\text{Role of } \text{ZnO} \text{ in Reaction 2}

\text{Conclusion}

The Sigma Insight: d-block Elements

The Dual Personality of Zinc Oxide

Analyzing the First Reaction

Analyzing the Second Reaction

The Final Verdict

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