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Structure of Atom question

2022 · Q134
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Structure of Atom question

2022 · Q134

NEETChemistryStructure of AtomMCQ+4 / −1

When electromagnetic radiation of wavelength 300 nm falls on the surface of a metal, electrons are emitted with the kinetic energy of 1.68 ×\times× 105 J mol−-−1. What is the minimum energy needed to remove an electron from the metal?

(h = 6.626 ×\times× 10−-−34 Js, c = 3 ×\times× 108 ms−-−1, NA = 6.022 ×\times× 1023 mol−-−1)

  1. A
    2.31 ×\times× 105 J mol−-−1
  2. B
    2.31 ×\times× 106 J mol−-−1
  3. C
    3.84 ×\times× 104 J mol−-−1
  4. D
    3.84 ×\times× 10−-−19 J mol−-−1
View written solutionFree

Correct answer: A

Energy of one photon $$ = {{hc} \over \lambda }$$ ($\lambda$ = 300 nm)

For one mole photons, $$E = {{hc} \over \lambda } \times {N_A}$$

$$E = {{6.626 \times {{10}^{ - 34}} \times 3 \times {{10}^8} \times 6.023 \times {{10}^{23}}} \over {300 \times {{10}^{ - 9}}}}$$

$$E = 3.99 \times {10^5}$$ J mol$-$1

Kinetic energy $ = 1.68 \times {10^5}$ J mol$-$1

${W_0} = E - K.E.$

$$ = 3.99 \times {10^5} - 1.68 \times {10^5}$$

$ = 2.31 \times {10^5}$ J mol$-$1

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