Question

One molecule of a substance absorbs one quantum of energy. The energy involved when $1.5$ mole of the substance absorbs red light of frequency $7.5\times {10}^{14}$ $se{c}^{-1}$ will be:

• A. $2.99\times {10}^5$J
• B. $3.23\times {10}^5$J
• C. $4.48\times {10}^5$J
• D. $2.99\times {10}^6$J

Answer 1

The correct option is C $4.48\times {10}^5$J

One molecule of a substance absorbs one quantum of energy.

$1$ mole= $6.023\times {10}^{23}$ atoms

$\therefore$ The energy involved in $1.5$ mole of the substance absorbs red light of frequency

$\gamma =7.5\times {10}^{14}se{c}^{-1}$

$E=N_{o}h\gamma$

$=1.5\times 6.023{\times }^{23}\times 6.626\times {10}^{-34}\times 7.5\times {10}^{14}$

$=4.48\times {10}^{5}J$ .