Activity 1.6 Class 10 Science

Aim of the activity

The activity aims to observe and identify the thermal decomposition of lead nitrate.

Material Required

1.   lead nitrate powder

2.   boiling tube

3.   tongs

4.   burner or spirit lamp

5.   safety goggles and gloves

Procedure

We will put about 2 g of lead nitrate powder in a clean, dry boiling tube. Now we hold the boiling tube with a pair of tongs and heat gently over the spirit lamp or burner flame.

Observations

Colour change – Initially, lead nitrate powder is white but on decomposition, a yellow residue is obtained.

Gas evolution—During heating, brown fumes emit from the tube, indicating gas evolution.

Nature of fumes – The brown fumes have a pungent smell that is characteristic of nitrogen dioxide gas.

Explanation

When we heat lead nitrate powder, it undergoes a thermal decomposition reaction and breaks down into simpler substances.

i.          A yellow-colored residue of lead oxide

ii.      Brown, pungent-smelling gas nitrogen dioxide

iii.    Colourless oxygen gas

These are the three substances formed after thermal decomposition.

Chemical reaction

`2Pb(NO_3)_2 →2PbO   + 4NO_2 + O_2`

Conclusion

This activity demonstrates the thermal decomposition of lead nitrate powder that produces lead oxide, nitrogen dioxide, and oxygen.

 

 

Safety Precautions

   1.  Always perform this activity in a well-ventilated area.

   2. Wear goggles and gloves.

   3. Use tongs to hold the boiling tube

Frequently Asked Questions

   1.  What type of chemical reaction takes place?

Ans – Thermal decomposition reaction takes place in this activity.

   2. What are the main products formed during the heating of lead nitrate?

Ans- Lead oxide, nitrogen dioxide, and oxygen

   3. What do brown fumes indicate?

Ans – The emission of brown fumes during the heating of lead nitrate indicates the release of nitrogen dioxide gas.

   4. What safety precautions should be taken during this activity?

Ans – (i) wear goggles and gloves

           (ii) hod the boiling tube with tongs

   5. What is the chemical formula of lead nitrate?

    Ans – Pb(NO3)2

     Important extra points

   1. Thermal decomposition reaction takes place. 

   2. A yellow residue of lead oxide is formed.

   3. Brown fumes of nitrogen dioxide gas are released.

You can also explore

   1.  Thermal decomposition of calcium carbonate

   2. Thermal decomposition of potassium chlorate