The energy absorbed by each molecule (A₂) of a substance is 4.4 × 10⁻¹⁹ J and bond energy per molecule is 4.0

Question

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:

Accepted Answer

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:**
    $$ 	ext{Excess Energy} = 	ext{Energy Absorbed} - 	ext{Bond Energy} $$
    $$ 	ext{Excess Energy} = (4.4 	imes 10^{-19} 	ext{ J}) - (4.0 	imes 10^{-19} 	ext{ J}) $$
    $$ 	ext{Excess Energy} = 0.4 	imes 10^{-19} 	ext{ J} = 4.0 	imes 10^{-20} 	ext{ J} $$

2.  **Calculate Kinetic Energy per Atom:**
    The molecule $A_2$ dissociates into 2 atoms. The total excess kinetic energy is shared equally between them.
    $$ 	ext{KE per atom} = \frac{	ext{Total Excess Energy}}{2} $$
    $$ 	ext{KE per atom} = \frac{4.0 	imes 10^{-20} 	ext{ J}}{2} = 2.0 	imes 10^{-20} 	ext{ J} $$

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