Problem 101 - A Complete Resource Book in Chemistry for JEE Main

Question

The correct order of acidic strength is (a) \(\mathrm{Cl}_{2} \mathrm{O}_{7}>\mathrm{SO}_{2}>\mathrm{P}_{4} \mathrm{O}_{10}\) (b) \(\mathrm{CO}_{2}>\mathrm{N}_{2} \mathrm{O}_{5}>\mathrm{SO}_{3}\) (c) \(\mathrm{Na}_{2} \mathrm{O}>\mathrm{MgO}>\mathrm{Al}_{2} \mathrm{O}_{3}\) (d) \(\mathrm{K}_{2} \mathrm{O}>\mathrm{CaO}>\mathrm{Mg} \mathrm{O}\)

Step-by-Step Solution

Answer

The correct order is (a) \( \mathrm{Cl}_{2}\mathrm{O}_{7}> \mathrm{SO}_{2}> \mathrm{P}_{4}\mathrm{O}_{10} \).

Step 1: Understand Acidic Oxides

Acidic oxides are typically formed by non-metals. The oxide becomes stronger in acidic nature with increasing electronegativity and oxidation state of the element. In general, oxides of nonmetals like P, S, and Cl tend to be acidic.

Step 2: Analyze Option (a)

Analyze the acidic strength order: - \(\mathrm{Cl}_{2}\mathrm{O}_{7}\) is a highly acidic oxide. - \(\mathrm{SO}_{2}\) is also acidic but weaker than \(\mathrm{Cl}_{2}\mathrm{O}_{7}\).- \(\mathrm{P}_{4}\mathrm{O}_{10}\) is less acidic than both.The order follows the typical trend of acidic oxides due to the increase in oxidation states from P to Cl.

Step 3: Analyze Option (b)

Examine the oxides: - \(\mathrm{CO}_{2}\) is acidic, \(\mathrm{N}_{2}\mathrm{O}_{5}\) is acidic, and \(\mathrm{SO}_{3}\) is also acidic.However, \(\mathrm{SO}_{3}\) is generally stronger than the others due to sulfur's higher oxidation state compared to carbon and nitrogen, so this order is incorrect.

Step 4: Analyze Option (c)

These are basic oxides.- \(\mathrm{Na}_{2}\mathrm{O}\) is strongly basic.- \(\mathrm{MgO}\) is less basic than \(\mathrm{Na}_{2}\mathrm{O}\).- \(\mathrm{Al}_{2}\mathrm{O}_{3}\) is amphoteric, not acidic or strongly basic.This order is incorrect for acidic strength.

Step 5: Analyze Option (d)

These oxides are basic, not acidic.- \(\mathrm{K}_{2}\mathrm{O}\) is more basic than \(\mathrm{CaO}\).- \(\mathrm{MgO}\) is less basic than the others.This sequence cannot be in order of acidic strength since they are basic.

Step 6: Choose the Correct Answer

Option (a) is correct as it follows the trend of increasing acidic strength with oxidation state.

Key Concepts

Acidic Oxides

Acidic oxides are compounds formed by the reaction of non-metals with oxygen. These oxides have the ability to produce an acidic solution when they interact with water. Non-metal oxides like sulfur dioxide (\(\mathrm{SO}_{2}\)) or chlorine heptoxide (\(\mathrm{Cl}_{2}\mathrm{O}_{7}\)) showcase acidic characteristics. When dissolved in water, these oxides tend to form acids. For example:

• \(\mathrm{SO}_{2} + \mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{H}_{2}\mathrm{SO}_{3}\) (sulfurous acid)
• \(\mathrm{Cl}_{2}\mathrm{O}_{7} + \mathrm{H}_{2}\mathrm{O} \rightarrow 2\mathrm{HClO}_{4}\) (perchloric acid)

The acidic strength of an oxide is generally associated with the element's electronegativity and oxidation state. As these factors increase, the acidic nature typically becomes stronger. It's important to distinguish between acidic oxides and basic oxides, as this will help you understand how these oxides modify their environment in chemical reactions.

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons. It plays a vital role in determining the behavior of elements and their compounds. Generally, non-metals have higher electronegativities compared to metals.For instance:

• Chlorine (Cl) is more electronegative than sulfur (S), which is evident in the acidic strength of their oxides (\(\mathrm{Cl}_{2}\mathrm{O}_{7}\) stronger than \(\mathrm{SO}_{2}\)).
• Electronegativity influences the polarity of bonds. More electronegative elements like chlorine form stronger acidic oxides due to their ability to attract electrons from oxygen.

Higher electronegativity usually leads to increased acidity because the oxide molecules are better at capturing a proton (H extsuperscript{+}) when dissolved in water. Understanding electronegativity helps predict how acidic or basic a particular oxide might be.

Oxidation State

The oxidation state of an element indicates the degree of oxidation or the loss of electrons. It is a significant factor affecting the acidic or basic nature of an oxide. Higher oxidation states typically correlate with stronger acidity. For example:

• In \(\mathrm{Cl}_{2}\mathrm{O}_{7}\), chlorine has an oxidation state of +7, which is higher than that in \(\mathrm{SO}_{2}\) where sulfur has an oxidation state of +4.
• This higher oxidation state helps elements attract oxygen atoms more effectively, leading to more acidic properties.

Understanding oxidation states can also help determine how a compound will interact in chemical reactions. Generally, compounds with elements in high oxidation states tend to be more reactive as they try to regain electrons to achieve stability.

Non-metal Oxides

Non-metal oxides are typically acidic as they form when non-metals react with oxygen. These oxides are crucial in showing the differences between metal oxides that are generally basic.Examples include:

• Carbon dioxide (\(\mathrm{CO}_{2}\))
• Sulfur trioxide (\(\mathrm{SO}_{3}\))
• Nitrogen pentoxide (\(\mathrm{N}_{2}\mathrm{O}_{5}\))

When non-metal oxides combine with water, they form acids that reflect the oxides' acidic characteristics.For instance:

• \(\mathrm{CO}_{2} + \mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{H}_{2}\mathrm{CO}_{3}\) (carbonic acid)
• \(\mathrm{N}_{2}\mathrm{O}_{5} + \mathrm{H}_{2}\mathrm{O} \rightarrow 2\mathrm{HNO}_{3}\) (nitric acid)

Understanding non-metal oxides allows us to predict the acidic nature of substances they form when interacting with other compounds, particularly water.