Thermal Decomposition of NH4Cl

The aim of this experiment is to study the thermal decomposition of ammonium chloride in an open container.

Thermal decomposition is the breakdown of a compound into simpler substances using heat. The decomposition of ammonium chloride takes place on heating to produce ammonia gas and hydrogen chloride.

NH₄Cl (s) ? NH₃(g) + HCl(g)

To perform this experiment, apparatus and materials are required: A tripod stand, wire gauze china dish, funnel, burner, filter paper, nessler’s reagent, ammonium chloride(s), blue litmus paper, distilled water.

The following procedure is required to perform this experiment.

In a china dish, take 5 g of ammonium chloride.
Place the funnel inverted over the china dish.
Heat this and observe for any change in the salt’s physical state.
The evolved gas is tested using a filter paper strip dipped in Nessler’s reagent.
Another test is done by using a moist blue litmus paper.
Changes in the colour for these are observed.

In this experiment, we heated ammonium chloride salt in a china dish, which undergoes thermal decomposition to form ammonia (NH₃) gas and hydrogen chloride (HCl) gas. This conversion process from solid directly to gas without first converting to liquid is known as sublimation.

The HCl gas evolved is tested using a moist blue litmus paper, which turns red. The NH₃ gas evolved is tested using a filter paper dipped in Nessler’s reagent, which turns brown.

FAQs on Thermal Decomposition of NH4Cl

Q1: What is the decomposition reaction?

Answer: Decomposition reactions are processes in which chemical species (reactants) are broken down into simpler substances.
For example: CaCO₃ ? CaO + CO₂

Q2. Explain sublimation with suitable examples.

Answer: Sublimation refers to a phenomenon of transformation or conversion of a substance from the solid phase into a gas phase without passing or changing through an intermediate liquid phase. For example, sublimation is dry ice which is a frozen form of carbon dioxide.

Q3: Na₂CO₃ ? Na₂O + CO₂
The above reaction is an example of a…………

1. Decomposition reaction
2. Neutralization reaction
3. Precipitation reaction

Answer: Decomposition. In the given reaction, Sodium carbonate undergoes decomposition to give sodium monoxide and carbon dioxide.

Q4: What is a balanced chemical equation?

Answer: A balanced equation is an equation for a chemical reaction in which the number of atoms for each element in the reaction and the total charge are the same for both the reactants and the products.