Q34 / 150 · MHT CET 2025 (23 Apr Shift 1) · Chemistry

What is the numerical value of angular momentum for an electron in first orbit of hydrogen atom ? ( $\mathrm{h}=6.626 \times 10^{-34} \mathrm{Js}$ )

  • Correct answer
    A
    $1.05 \times 10^{-34}$
  • B
    $2 \cdot 10 \times 10^{-34}$
  • C
    $3.16 \times 10^{-34}$
  • D
    $4.22 \times 10^{-34}$

Solution

The angular momentum of an electron in Bohr's stationary orbit is quantized as $L = n\frac{h}{2\pi}$, where $n$ is the principal quantum number and $h$ is Planck's constant ($6.626 \times 10^{-34} \mathrm{Js}$).

For the first orbit, $n = 1$, yielding $L = \frac{6.626 \times 10^{-34}}{2\pi} \mathrm{Js}$.

Numerical evaluation gives $L \approx 1.0545 \times 10^{-34} \mathrm{Js}$, which rounds to $1.05 \times 10^{-34} \mathrm{Js}$.

This matches option A.

Hence, the correct answer is option: 'A'.

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