Problem 82
Question
What is the anhydride for each of the following acids: (a) \(\mathrm{H}_{2} \mathrm{SO}_{4},(\mathbf{b}) \mathrm{HClO}_{3},(\mathbf{c}) \mathrm{HNO}_{2},\) (d) \(\mathrm{H}_{2} \mathrm{CO}_{3},(\mathbf{e}) \mathrm{H}_{3} \mathrm{PO}_{4} ?\)
Step-by-Step Solution
Verified Answer
The anhydrides for the given acids are:
(a) \(\mathrm{H}_{2} \mathrm{SO}_{4}: \mathrm{H}_{2}\mathrm{S}_{2}\mathrm{O}_{7}\)
(b) \(\mathrm{HClO}_{3}: \mathrm{Cl}_{2}\mathrm{O}_{6}\)
(c) \(\mathrm{HNO}_{2}: \mathrm{N}_{2}\mathrm{O}_{3}\)
(d) \(\mathrm{H}_{2} \mathrm{CO}_{3}:\) No stable anhydride
(e) \(\mathrm{H}_{3} \mathrm{PO}_{4}: \mathrm{H}_{4}\mathrm{P}_{2}\mathrm{O}_{7}\)
1Step 1: Understand the process of forming anhydrides
To form an anhydride from an acid, you need to remove one water molecule (H2O) from two molecules of the acid and then combine the remaining elements together. This will yield the corresponding anhydride.
2Step 2: Find the anhydride for \(\mathrm{H}_{2} \mathrm{SO}_{4}\)
Remove one water molecule (H2O) from two molecules of \(\mathrm{H}_{2} \mathrm{SO}_{4}\):
\(\mathrm{2H}_{2} \mathrm{SO}_{4} - \mathrm{H}_{2}\mathrm{O}\)
Combine the remaining elements to get the anhydride:
\(\mathrm{H}_{2}\mathrm{S}_{2}\mathrm{O}_{7}\)
The anhydride for \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is \(\mathrm{H}_{2}\mathrm{S}_{2}\mathrm{O}_{7}\).
3Step 3: Find the anhydride for \(\mathrm{HClO}_{3}\)
Remove one water molecule (H2O) from two molecules of \(\mathrm{HClO}_{3}\):
\(\mathrm{2HClO}_{3} - \mathrm{H}_{2}\mathrm{O}\)
Combine the remaining elements to get the anhydride:
\(\mathrm{Cl}_{2}\mathrm{O}_{6}\)
The anhydride for \(\mathrm{HClO}_{3}\) is \(\mathrm{Cl}_{2}\mathrm{O}_{6}\).
4Step 4: Find the anhydride for \(\mathrm{HNO}_{2}\)
Remove one water molecule (H2O) from two molecules of \(\mathrm{HNO}_{2}\):
\(\mathrm{2HNO}_{2} - \mathrm{H}_{2}\mathrm{O}\)
Combine the remaining elements to get the anhydride:
\(\mathrm{N}_{2}\mathrm{O}_{3}\)
The anhydride for \(\mathrm{HNO}_{2}\) is \(\mathrm{N}_{2}\mathrm{O}_{3}\).
5Step 5: Find the anhydride for \(\mathrm{H}_{2} \mathrm{CO}_{3}\)
\(\mathrm{H}_{2}\mathrm{CO}_{3}\) doesn't produce a stable anhydride. When you try to remove a water molecule from two molecules of \(\mathrm{H}_{2}\mathrm{CO}_{3}\), it will simply decompose into water and carbon dioxide.
6Step 6: Find the anhydride for \(\mathrm{H}_{3} \mathrm{PO}_{4}\)
Remove one water molecule (H2O) from two molecules of \(\mathrm{H}_{3} \mathrm{PO}_{4}\):
\(\mathrm{2H}_{3} \mathrm{PO}_{4} - \mathrm{H}_{2}\mathrm{O}\)
Combine the remaining elements to get the anhydride:
\(\mathrm{H}_{4}\mathrm{P}_{2}\mathrm{O}_{7}\)
The anhydride for \(\mathrm{H}_{3} \mathrm{PO}_{4}\) is \(\mathrm{H}_{4}\mathrm{P}_{2}\mathrm{O}_{7}\).
To summarize, the anhydrides for the given acids are as follows:
(a) \(\mathrm{H}_{2} \mathrm{SO}_{4}: \mathrm{H}_{2}\mathrm{S}_{2}\mathrm{O}_{7}\)
(b) \(\mathrm{HClO}_{3}: \mathrm{Cl}_{2}\mathrm{O}_{6}\)
(c) \(\mathrm{HNO}_{2}: \mathrm{N}_{2}\mathrm{O}_{3}\)
(d) \(\mathrm{H}_{2} \mathrm{CO}_{3}:\) No stable anhydride
(e) \(\mathrm{H}_{3} \mathrm{PO}_{4}: \mathrm{H}_{4}\mathrm{P}_{2}\mathrm{O}_{7}\)
Key Concepts
Acid AnhydridesDehydration ReactionsInorganic Chemistry
Acid Anhydrides
Acid anhydrides are intriguing compounds in chemistry often derived by removing a water molecule from an acid. To put it simply, when you have two molecules of an acid and take away a single molecule of water (H2O), what remains is typically an acid anhydride. This process can be easily compared to dehydration reactions. By combining leftover molecules after water removal, acid anhydrides are formed.
An example is sulfuric acid ( H2SO4 ). Removing water from two sulfuric acid molecules leaves behind H2S2O7, the anhydride of sulfuric acid. Similarly, we can do this with chloric acid (HClO3), resulting in Cl2O6. Not every acid has a stable anhydride like carbonic acid (H2CO3), which decomposes rather than forming an anhydride.
Key points to remember about acid anhydrides:
An example is sulfuric acid ( H2SO4 ). Removing water from two sulfuric acid molecules leaves behind H2S2O7, the anhydride of sulfuric acid. Similarly, we can do this with chloric acid (HClO3), resulting in Cl2O6. Not every acid has a stable anhydride like carbonic acid (H2CO3), which decomposes rather than forming an anhydride.
Key points to remember about acid anhydrides:
- They are created by removing water from acids.
- Not all acids will form stable anhydrides upon dehydration.
- These reactions highlight the relationship between acids and their anhydrides.
Dehydration Reactions
Dehydration reactions play a critical role in the formation of acid anhydrides. These reactions are aptly named because they involve the removal of water from compounds. In the context of chemistry, especially with acids, dehydration is used to systematically calculate and derive an anhydride from its respective acid.
How do dehydration reactions work in this context?
Taking two similar acid molecules and removing one unit of water, dehydration reactions help in rearranging the remaining molecules, forming a new, typically more complex compound, known as an anhydride. This chemically intelligent process exemplifies how molecules interact upon losing small constituents like H2O.
This is a key intermediate reaction type in acid chemistry and gives insight into molecular stability changes. Remember:
How do dehydration reactions work in this context?
Taking two similar acid molecules and removing one unit of water, dehydration reactions help in rearranging the remaining molecules, forming a new, typically more complex compound, known as an anhydride. This chemically intelligent process exemplifies how molecules interact upon losing small constituents like H2O.
This is a key intermediate reaction type in acid chemistry and gives insight into molecular stability changes. Remember:
- Dehydration reactions are instrumental in forming anhydrides.
- Not all reactions will occur naturally or successfully.
- Understanding dehydration offers insight into various chemical synthesis processes.
Inorganic Chemistry
Inorganic chemistry is a vast field that covers a wide array of non-organic substances, including acids and anhydrides. This branch of chemistry delves into materials that do not contain carbon-hydrogen bonds, distinct from organic chemistry.
A myriad of topics fall under inorganic chemistry, but acid anhydrides make for a fascinating subject. These compounds form a bridge between simple acids and their more complex anhydride counterparts. Understanding how anhydrides form gives students a clear view of the reactions occurring in inorganic settings.
For example, when analyzing nitrogen dioxide (NO2), a common compound, inorganic chemistry explains how N2O3 is derived from nitrous acid (HNO2). It also illustrates the limitations such as the instability seen in supposed anhydrides of certain compounds like carbonic acid (H2CO3).
Key aspects of inorganic chemistry for students:
A myriad of topics fall under inorganic chemistry, but acid anhydrides make for a fascinating subject. These compounds form a bridge between simple acids and their more complex anhydride counterparts. Understanding how anhydrides form gives students a clear view of the reactions occurring in inorganic settings.
For example, when analyzing nitrogen dioxide (NO2), a common compound, inorganic chemistry explains how N2O3 is derived from nitrous acid (HNO2). It also illustrates the limitations such as the instability seen in supposed anhydrides of certain compounds like carbonic acid (H2CO3).
Key aspects of inorganic chemistry for students:
- Focus on understanding compounds without carbon-hydrogen bonds.
- Study of molecular interaction to predict behaviors like decomposition or anhydride formation.
- Insight into the intricate orchestration of elements outside the organic realm.
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