Show by a chemical reaction with water that $Na_2O$ is a basic oxide and $Cl_2O_7$ is an acidic oxide.

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> [!TLDR]
> Basic oxides react with water to form bases (alkalis), while acidic oxides react with water to form acids. $Na_2O$ gives NaOH (a base), and $Cl_2O_7$ gives $HClO_4$ (an acid), confirming their nature.

The classification of oxides as acidic or basic depends on how they behave with water. A **basic oxide** is one that reacts with water to produce a base (a hydroxide that releases $OH^-$ ions). An **acidic oxide** reacts with water to produce an acid (a compound that releases $H^+$ ions). This is a direct chemical test — no need for pH paper or indicators; just look at the product.

Metal oxides tend to be basic, especially those of highly electropositive metals like sodium. Non-metal oxides tend to be acidic, especially those of elements in higher oxidation states, like chlorine in $Cl_2O_7$.

Let’s verify each with its reaction.

1. **$Na_2O$ with water**  
   Sodium oxide is an ionic compound containing $Na^+$ and $O^{2-}$ ions. When added to water, the oxide ion ($O^{2-}$) is strongly basic — it pulls a proton from water to form two hydroxide ions.  
   The balanced equation is:  
   $$Na_2O(s) + H_2O(l) \rightarrow 2NaOH(aq)$$  
   Sodium hydroxide ($NaOH$) is a strong base — it dissociates completely in water to give $Na^+$ and $OH^-$ ions. The solution turns red litmus blue and has a pH > 7. Because the product is a base, $Na_2O$ is a **basic oxide**.

2. **$Cl_2O_7$ with water**  
   Dichlorine heptoxide is a covalent molecule where chlorine is in its highest oxidation state (+7). It is the anhydride of perchloric acid. When it reacts with water, it adds across the O–H bonds to form two molecules of a strong acid.  
   The balanced equation is:  
   $$Cl_2O_7(l) + H_2O(l) \rightarrow 2HClO_4(aq)$$ …

Type	Made from	Reacts with water to give	Example
Acidic oxide	Non-metals	Acid	$CO_2$ , $SO_2$ , $SO_3$ , $NO_2$ , $P_2O_5$
Basic oxide	Metals	Base	$Na_2O$ , $CaO$ , $MgO$ , $K_2O$ , $CuO$

Q.Show by a chemical reaction with water that $Na_2O$ is a basic oxide and $Cl_2O_7$ is an acidic oxide.

Concept understanding — Acidic And Basic Oxides

What Are Acidic and Basic Oxides? Let's Start With What You Already Know

The Intuition: It's About the Element's "Personality"

The Precise Definitions

Acidic Oxide

Basic Oxide

The Big Picture: A Simple Table

Why This Matters for Exams

Q.Show by a chemical reaction with water that Na2ONa_2ONa2​O is a basic oxide and Cl2O7Cl_2O_7Cl2​O7​ is an acidic oxide.

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Q.Show by a chemical reaction with water that $Na_2O$ is a basic oxide and $Cl_2O_7$ is an acidic oxide.

Unlock everything free for 14 days