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Activity 1.6: Ncert book Science class 10
In this article, we will explore Activity 1.6 from Chapter 1 of the Class 10 Science NCERT book, which focuses on the heating of lead nitrate and the emission of nitrogen dioxide.
Activity 1.6 for Class 10 Science
Objective
The primary aim of Activity 1.6 is to observe and understand the changes that occur when lead nitrate is heated.
Theory
Decomposition Reactions
Decomposition reactions involve breaking down a compound into simpler substances, often requiring an input of energy. Activity 1.6 demonstrates a thermal decomposition reaction, where heat drives the breakdown of lead nitrate.
Role of Heat
Heating a substance causes its particles to vibrate more rapidly, weakening and breaking atomic bonds. In lead nitrate, heating supplies the energy needed to break its bonds, resulting in new products.
The Products of the Reaction
The heating of lead nitrate results in the following chemical reaction:
$2Pb(NO_3)_ (s) \rightarrow 2PbO (s) + 4NO_2 (g) + O_2 (g)$
Heating lead nitrate causes it to decompose into lead oxide $(PbO)$, nitrogen dioxide $(NO_2)$, and oxygen $(O_2)$. $PbO$ is a yellow, dense, and water-insoluble powder with amphoteric properties. $NO_2$ is a reddish-brown, toxic gas and a primary air pollutant. $O_2$ is a colorless, odorless, and tasteless gas essential for life.
Materials Required
- 2 g lead nitrate powder
- A boiling tube
- A pair of tongs
- A flame source
Safety Precautions
- Always wear safety goggles and gloves while performing this experiment.
- Ensure proper ventilation, as nitrogen dioxide is a toxic gas.
- Handle the boiling tube with care, as it will become very hot during the experiment.
- Dispose of the lead oxide residue according to the guidelines provided by your teacher or laboratory supervisor.
Procedure
Step 1: Measure approximately 2 g of lead nitrate powder and place it inside the boiling tube.
Step 2: Hold the boiling tube firmly using a pair of tongs to ensure safety while heating.
Step 3: Heat the boiling tube containing the lead nitrate powder over a flame, as depicted in Figure given below.
Observations
As you heat the lead nitrate powder, you’ll notice that it starts to decompose. A change in color is observed, as a brownish gas is released from the boiling tube. This gas is nitrogen dioxide (NO2). Meanwhile, a yellow residue is left behind in the boiling tube, which is lead oxide $(PbO)$.
Chemical Reaction
The heating of lead nitrate results in the following chemical reaction:
$2Pb(NO_3)_ (s) \rightarrow 2PbO (s) + 4NO_2 (g) + O_2 (g)$
In this reaction, lead nitrate $(Pb(NO_3)_2)$ decomposes into lead oxide $(PbO)$, nitrogen dioxide $(NO_2)$, and oxygen $(O_2)$. The brownish gas observed during the experiment is nitrogen dioxide, while the yellow residue left behind is lead oxide.