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Structure of Atom question

2024 · 5 Apr · Shift 1 · Q27
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  5. /2024 · 5 Apr · Shift 1 · Q27

Structure of Atom question

2024 · 5 Apr · Shift 1 · Q27

JEE MainChemistryStructure of AtomNumerical+4 / −1
The value of Rydberg constant (RH)(R_H)(RH​) is 2.18×10−18 J2.18 \times 10^{-18} \mathrm{~J}2.18×10−18 J. The velocity of electron having mass 9.1×10−31 kg9.1 \times 10^{-31} \mathrm{~kg}9.1×10−31 kg in Bohr's first orbit of hydrogen atom = ‾\underline{\hspace{2cm}}​×105 ms−1\times 10^5 \mathrm{~ms}^{-1}×105 ms−1 (nearest integer).
Numerical answer
View written solutionFree

Correct answer: 22

  1. Use Bohr model energy relation

For hydrogen atom, the total energy in the first orbit is E1=−2.18×10−18 JE_1=-2.18\times 10^{-18}\,\text{J}E1​=−2.18×10−18J

The given value called Rydberg constant here is actually the magnitude of ground-state energy.

In Bohr model, K=−EK = -EK=−E where KKK is kinetic energy.

So, K=2.18×10−18 JK = 2.18\times 10^{-18}\,\text{J}K=2.18×10−18J

  1. Write kinetic energy in terms of velocity

K=12mv2K=\frac{1}{2}mv^2K=21​mv2

Thus, 12(9.1×10−31)v2=2.18×10−18\frac{1}{2}(9.1\times 10^{-31})v^2=2.18\times 10^{-18}21​(9.1×10−31)v2=2.18×10−18

  1. Solve for v2v^2v2

v2=2×2.18×10−189.1×10−31v^2=\frac{2\times 2.18\times 10^{-18}}{9.1\times 10^{-31}}v2=9.1×10−312×2.18×10−18​

v2=4.369.1×1013v^2=\frac{4.36}{9.1}\times 10^{13}v2=9.14.36​×1013

v2≈0.4791×1013v^2\approx 0.4791\times 10^{13}v2≈0.4791×1013

v2≈4.791×1012v^2\approx 4.791\times 10^{12}v2≈4.791×1012

  1. Take square root

v=4.791×1012v=\sqrt{4.791\times 10^{12}}v=4.791×1012​

v≈2.19×106 m s−1v\approx 2.19\times 10^6\,\text{m s}^{-1}v≈2.19×106m s−1

  1. Express in the required form

We need v=(number)×105 m s−1v = (\text{number})\times 10^5\,\text{m s}^{-1}v=(number)×105m s−1

So, 2.19×106=21.9×1052.19\times 10^6 = 21.9\times 10^52.19×106=21.9×105

Nearest integer =22=22=22.

Final Answer

22\boxed{22}22​

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