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NEET CHEMISTRYEasy

The energy absorbed by each molecule (A₂) of a substance is 4.4 × 10⁻¹⁹ J and bond energy per molecule is 4.0 × 10⁻¹⁹ J. The kinetic energy of the molecule per atom will be:

A

2.2 × 10⁻¹⁹ J

B

2.0 × 10⁻¹⁹ J

C

2.0 × 10⁻²⁰ J

D

4.0 × 10⁻²⁰ J

Step-by-Step Solution

When a molecule absorbs energy, a portion of it is used to break the chemical bond (bond energy), and the remaining excess energy is converted into the kinetic energy of the constituent atoms.

  1. Calculate Total Excess Energy: Excess Energy=Energy Absorbed−Bond Energy\text{Excess Energy} = \text{Energy Absorbed} - \text{Bond Energy} Excess Energy=(4.4×10−19 J)−(4.0×10−19 J)\text{Excess Energy} = (4.4 \times 10^{-19} \text{ J}) - (4.0 \times 10^{-19} \text{ J}) Excess Energy=0.4×10−19 J=4.0×10−20 J\text{Excess Energy} = 0.4 \times 10^{-19} \text{ J} = 4.0 \times 10^{-20} \text{ J}

  2. Calculate Kinetic Energy per Atom: The molecule A2A_2 dissociates into 2 atoms. The total excess kinetic energy is shared equally between them. KE per atom=Total Excess Energy2\text{KE per atom} = \frac{\text{Total Excess Energy}}{2} KE per atom=4.0×10−20 J2=2.0×10−20 J\text{KE per atom} = \frac{4.0 \times 10^{-20} \text{ J}}{2} = 2.0 \times 10^{-20} \text{ J}

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