Problem 6 - Basic Principles of Organic Chemistry

Question

Write balanced equations for the reactions of (a) ammonia with sulfuric acid, (b) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}\) with sulfuric acid, (c) sodium hydroxide with ammonium chloride, and (d) sodium hydroxide with \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{3} \stackrel{\ominus}{\mathrm{C}} 1\).

Step-by-Step Solution

Answer

(a) 2NH₃ + H₂SO₄ → (NH₄)₂SO₄; (b) 2C₂H₅NH₂ + H₂SO₄ → (C₂H₅NH₃)₂SO₄; (c) NaOH + NH₄Cl → NaCl + H₂O + NH₃; (d) C₂H₅NH₃Cl + NaOH → C₂H₅NH₂ + NaCl + H₂O.

Step 1: Balance ammonia with sulfuric acid

Ammonia (\( \mathrm{NH}_3 \)) reacts with sulfuric acid (\( \mathrm{H}_2\mathrm{SO}_4 \)) to form ammonium sulfate. The balanced chemical equation is: \[ 2\ \mathrm{NH}_3\ (aq) + \ \mathrm{H}_2\mathrm{SO}_4\ (aq) \rightarrow \ \left(\mathrm{NH}_4\right)_2\mathrm{SO}_4\ (aq)\] Two molecules of ammonia combine with one molecule of sulfuric acid to produce one molecule of ammonium sulfate.

Step 2: Balance CH₃CH₂NH₂ with sulfuric acid

Ethanamine (\( \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_2 \)) reacts with sulfuric acid (\( \mathrm{H}_2\mathrm{SO}_4 \)) to form ethylammonium sulfate. The balanced chemical equation is:\[ 2\ \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_2\ (aq) + \ \mathrm{H}_2\mathrm{SO}_4\ (aq) \rightarrow \ \left(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_3\right)_2\mathrm{SO}_4\ (aq)\] Two molecules of ethanamine react with one molecule of sulfuric acid to produce one molecule of ethylammonium sulfate.

Step 3: Balance sodium hydroxide with ammonium chloride

Sodium hydroxide (\( \mathrm{NaOH} \)) reacts with ammonium chloride (\( \mathrm{NH}_4\mathrm{Cl} \)) to produce sodium chloride, water, and ammonia gas. The balanced equation is: \[ \mathrm{NaOH} \ (aq) + \ \mathrm{NH}_4\mathrm{Cl} \ (aq) \rightarrow \ \mathrm{NaCl} \ (aq) + \ \mathrm{H}_2\mathrm{O} \ (l) + \ \mathrm{NH}_3 \ (g)\] One molecule of sodium hydroxide reacts with one molecule of ammonium chloride to produce one molecule each of sodium chloride, water, and gas ammonia.

Step 4: Balance sodium hydroxide with CH₃CH₂NH₃C₁

Sodium ethylammonium (\( \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_3\stackrel{\ominus}{\mathrm{Cl}} \)) reacts with sodium hydroxide (\( \mathrm{NaOH} \)) to produce ethylamine, sodium chloride, and water. The balanced equation is:\[ \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_3\stackrel{\ominus}{\mathrm{Cl}} \ (aq) + \ \mathrm{NaOH} \ (aq) \rightarrow \ \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_2 \ (aq) + \ \mathrm{NaCl} \ (aq) + \ \mathrm{H}_2\mathrm{O} \ (l)\]One molecule of sodium ethylammonium chloride reacts with one molecule of sodium hydroxide to produce one molecule each of ethylamine, sodium chloride, and water.

Key Concepts

Balanced Equations

Chemical reactions often involve the transformation of substances into new products. Balancing equations is crucial because it reflects the conservation of mass. In other words, the number of atoms for each element must remain the same before and after a reaction.
A balanced equation ensures that reactions comply with the law of conservation of mass. For example, when balancing ammonia (\( \mathrm{NH}_3 \)) with sulfuric acid (\( \mathrm{H}_2\mathrm{SO}_4 \)) to form ammonium sulfate (\( \left(\mathrm{NH}_4\right)_2\mathrm{SO}_4 \)), we have:

• 2 molecules of \( \mathrm{NH}_3 \) react with 1 molecule of \( \mathrm{H}_2\mathrm{SO}_4 \).
• This yields 1 molecule of \( \left(\mathrm{NH}_4\right)_2\mathrm{SO}_4 \).

This reflects the importance of getting the same number of each type of atom on both sides of the equation. Balancing involves adjusting coefficients, the numbers in front of molecules, rather than changing subscripts, which would alter the substances themselves. This keeps chemical identities intact while ensuring mass conservation.

Acid-Base Reactions

Acid-base reactions involve the transfer of protons (\( \mathrm{H}^+ \)) between reactants. Understanding these reactions is vital as they are common in both laboratory and everyday situations.
When ammonia, a weak base, reacts with sulfuric acid, a strong acid, it forms ammonium sulfate through the following balanced equation:

• \[ 2\ \mathrm{NH}_3\ (aq) + \ \mathrm{H}_2\mathrm{SO}_4\ (aq) \rightarrow \ \left(\mathrm{NH}_4\right)_2\mathrm{SO}_4\ (aq)\]

Here, ammonia accepts protons from sulfuric acid, emphasizing its role as a base. In reactions involving sodium hydroxide, a strong base, with acidic compounds such as ammonium chloride, there is a release of ammonia gas:

• \[ \mathrm{NaOH} \ (aq) + \ \mathrm{NH}_4\mathrm{Cl} \ (aq) \rightarrow \ \mathrm{NaCl} \ (aq) + \ \mathrm{H}_2\mathrm{O} \ (l) + \ \mathrm{NH}_3 \ (g)\]

This displays the classic acid-base interaction where new compounds, sodium chloride and water, are formed.

Ammonia Reactions

Ammonia is a key player in various chemical reactions due to its basic nature. It is involved in producing important compounds either in the industry or the laboratory.
In the reaction with sulfuric acid, ammonia forms ammonium sulfate, a valuable salt used in fertilizers:

• \[ 2\ \mathrm{NH}_3\ (aq) + \ \mathrm{H}_2\mathrm{SO}_4\ (aq) \rightarrow \ \left(\mathrm{NH}_4\right)_2\mathrm{SO}_4\ (aq)\]

When sodium hydroxide reacts with ammonium chloride, it results in ammonia gas release, as well as sodium chloride and water:

• \[ \mathrm{NaOH} \ (aq) + \ \mathrm{NH}_4\mathrm{Cl} \ (aq) \rightarrow \ \mathrm{NaCl} \ (aq) + \ \mathrm{H}_2\mathrm{O} \ (l) + \ \mathrm{NH}_3 \ (g)\]

This demonstrates ammonia's versatility in shifting between gas and solid forms, depending on the reactions it takes part in.

Organic Chemistry

Organic chemistry contributes to understanding the reactions of complex molecules that contain carbon and hydrogen. Ethanamine, for example, is a simple organic compound that reacts with acids like sulfuric acid.
In its reaction with sulfuric acid, ethanamine forms ethylammonium sulfate through a balanced chemical equation:

• \[ 2\ \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_2\ (aq) + \ \mathrm{H}_2\mathrm{SO}_4\ (aq) \rightarrow \ \left(\mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_3\right)_2\mathrm{SO}_4\ (aq)\]

This illustrates the ability of organic compounds to form new substances when interacting with other chemicals. Similarly, when ethylammonium chloride interacts with sodium hydroxide, it produces ethylamine, reinforcing organic molecules' dynamic interchangeability:

• \[ \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_3\stackrel{\ominus}{\mathrm{Cl}} \ (aq) + \ \mathrm{NaOH} \ (aq) \rightarrow \ \mathrm{CH}_{3}\mathrm{CH}_{2}\mathrm{NH}_2 \ (aq) + \ \mathrm{NaCl} \ (aq) + \ \mathrm{H}_2\mathrm{O} \ (l)\]

Organic chemistry often focuses on the transformation of organic molecules through such reactions, emphasizing their versatility in different chemical environments.