Ammonia - Structure, Preparation, Uses, FAQs

Characteristics of Ammonia Gas - $\mathrm{NH}_3$

The compound ammonia gas is known as a weak base since it forms ammonia salts when combined with a variety of acids. The result of the reaction between ammonia gas and hydrochloric acid is ammonium chloride. The ammonium cation NH₄⁺ is found in all ammonia salts produced through such acid-base reactions. Liquid ammonia has also been found to possess weak acidic properties and, therefore, can be considered an amphoteric compound. With some alkali metals and alkaline earth metals, ammonia forms amides due to its acidic qualities. The NH₃ molecule is also known to undergo self-dissociation once it is dissolved in water. Ammonia molecules undergo molecular autoionization, which forms their conjugate bases (NH₂^–) and acids (NH₄⁺). Below is an illustration of the structure of the ammonium cation.

Structure of Ammonia $\mathrm{NH}_3$

Ammonia (NH₃) has a trigonal pyramidal structure, formed by one nitrogen atom and three hydrogen atoms. The nitrogen atom is sp³ hybridized, with three of its hybrid orbitals forming σ (sigma) bonds with hydrogen atoms, and the fourth containing a lone pair of electrons.

Because of this lone pair, the molecule is not planar the lone pair repels the N–H bonds, giving ammonia its pyramidal shape.

Preparation of Ammonia

Sodium hydroxide or calcium hydroxide are powerful alkalis which are used to prepare ammonia in the laboratory.

$2 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{Ca}(\mathrm{OH})_2 \rightarrow \mathrm{CaCl}_2+2 \mathrm{H}_2 \mathrm{O}+2 \mathrm{NH}_3(\mathrm{~g})$

Alternatively, the gas can be made by heating concentrated ammonium hydroxide.

Under high pressure and the presence of a catalyst, nitrogen and hydrogen are directly combined to produce ammonia in the Haber Process.

Uses of Ammonia ($\mathrm{NH}_3$)

• Fertilizing crops with it produces higher yields

• As a cleaner, stainless steel and glass can be cleaned with NH₃ inside a home

• Food products containing it provide antimicrobial properties

• There are many industries that use it for fermentation

• The refrigerant used in refrigeration is this

• The pH of fermentation processes must be adjusted

• Hence, it neutralizes emissions of diesel engine pollutants such as nitrogen oxides

• For rocket engines, it is used as a fuel

• In textile industries, it is used

• For manufacturing synthetic fibres like rayon and nylon

Also Read :

Some Solved Examples

Question 1: Identify the products when chlorine react with excess ammonia
1) $\mathrm{NCl}_3$ and HCl
2) $\mathrm{NCl}_3$ and $\mathrm{N}_2$
3) (correct) $\mathrm{NH}_4 \mathrm{Cl}$ and $\mathrm{N}_2$
4) $\mathrm{NCl}_3$ and $\mathrm{NH}_4 \mathrm{Cl}$

Solution:

As we learned

Reaction with Ammonia in excess Chlorine -

$\mathrm{NH}_3+3 \mathrm{Cl}_2 \rightarrow \mathrm{NCl}_3+3 \mathrm{HCl}$

wherein
$\mathrm{NCl}_3$ is an explosive

$8 \mathrm{NH}_3+\mathrm{cl}_2 \rightarrow 6 \mathrm{NH}_4 \mathrm{cl}+\mathrm{N}_2$

Hence the answer is the option (3).

Question 2: Which property of $\mathrm{NH}_3$ is shown in the following reaction-

$\mathrm{NH}_3+\mathrm{CuO} \rightarrow$

1) (correct) Reducing property
2) Oxidising property
3) Basic Property
4) Acidic property

Solution:

As we learn

Ammonia as a reducing agent -
Reduces heated CuO and $\mathrm{Cl}_2$
wherein

$\begin{aligned}
& 2 \mathrm{NH}_3+3 \mathrm{CuO} \xrightarrow{\Delta} 3 \mathrm{Cu}+3 \mathrm{H}_2 \mathrm{O}+\mathrm{N}_2 \\
& 2 \mathrm{NH}_3+3 \mathrm{CuO} \rightarrow 3 \mathrm{Cu}+\mathrm{N}_2+3 \mathrm{H}_2 \mathrm{O}
\end{aligned}$

$\mathrm{NH}_3$ is a reducing agent while CuO is an oxidising agent.
Hence, the answer is the option (1).

Question 3: Which is a very good solvent for alkali metals.
1) Liquid $\mathrm{SO}_2$
2) Liquid Ozone
3) (correct) Liquid $\mathrm{NH}_3$
4) Liquid $\mathrm{H}_2 \mathrm{O}$

Solution:

As we learn

Manufacture of ammonia by Calcium Cyanamide -
$\mathrm{CaCN}_2$ is hydrolysed with superheated steam
wherein

$\begin{aligned}
& \mathrm{CaC}_2+\mathrm{N}_2 \xrightarrow{\Delta} \mathrm{CaCN}_2+\mathrm{C} \\
& \mathrm{CaCN}_2+3 \mathrm{H}_2 \mathrm{O} \xrightarrow{450 \mathrm{~K}} \mathrm{CaCO}_3+2 \mathrm{NH}_3
\end{aligned}$

liq. $\mathrm{NH}_3$ is a very good solvent for alkali metals and alkaline earth metals.

$\text { example : } \mathrm{Na}+(x+y) \mathrm{NH}_3 \rightarrow\left[\mathrm{Na}\left(\mathrm{NH}_3\right)_x\right]+\left[e\left(\mathrm{NH}_3\right)_y\right]$
Hence, the answer is option (3).

Question 4: Which gas is produced by the decay of nitrogenous organic matter, like urea:

1) NO

2) NO₂

3) N₂O

4) (correct) NH₃

Solution:

As we learn

Production of ammonia -

$\begin{aligned}
& \mathrm{CaCN}_2+3 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{CaCO}_3+2 \mathrm{NH}_3 \\
& \mathrm{AlN}+3 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Al}(\mathrm{OH})_3+\mathrm{NH}_3
\end{aligned}$
Decay of urea produces ammonia,

$\mathrm{NH}_2 \mathrm{CONH}_2+2 \mathrm{H}_2 \mathrm{O} \rightarrow\left(\mathrm{NH}_4\right)_2 \mathrm{CO}_3 \rightleftharpoons 2 \mathrm{NH}_3+\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O}$
Hence, the answer is option (4).

Question 5: The hybridization and shape of $\mathrm{NH}_3$ molecule are respectively.
1) $s p^2$, tetrahedral
2) $s p^3$, tetrahedral
3) $s p^2$, Planar
4) (correct) $s p^3$, pyramidal

Solution:

As we learn

Structure of Ammonia -

N atom is sp³ hybridized with a love pair of electrons. Pyramidal in shape.

N:

$s p^3$ hybrid

Shape: Pyramidal

Hence, the answer is option (4).

Practice more questions with the link given below: