Question:

If the uncertainty in velocity and position of a minute particle in space are, \(2.4 × 10^{–26}\) \((m s^{–1)}\) and \(10^{–7} (m)\), respectively. The mass of the particle in g is _____ . (Nearest integer)
(Given : \(h = 6.626 × 10^{–34} Js\))

Updated On: Aug 5, 2024
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Correct Answer: 22

Solution and Explanation

\(Δv = 2.4 \times 10-26 \ ms^{-1}\)
\(Δx = 10^{-7} m\)
By uncertainty principle,
\(∴ m ≥ \frac {h}{4\pi(Δx)(Δv)}\)

\(m≥ \frac {6.626 \times 10^{-34}}{4\times 3.14 \times (10^{-7})(2.4)\times 10^{-26}}\)

\(m≥ \frac {6.626 \times 10^{-1}}{4 \times 2.4\times3.14}\)

\(m≥ 0.02198\ kg\)
\(m≥ 21.98\ g\)

So, the mass of the particle \(≃ 22\ g\)

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Concepts Used:

Uncertainty in Measurement

  • Atoms and molecules consist of very low mass. But they are present in huge numbers.
  • Chemists have to deal with numbers as large as 602,200,000,000,000,000,000,000, which is the number of molecules of 2g of hydrogen.
  • There are even other constants like the speed of light, charges on particles, Avogadro’s number and etc.
  • To handle these large or small numbers, we use the following notation: m × 10n, which is, m times ten raised to the power of n. In this expression, n is an exponent having positive and negative values and m is that number that varies from 1.000… and 9.999…
  • The scientific notation 573.672 can be written as 5.73672 × 10 and in the same way, 0.000089 can also be written as 8.9 × 10-5.
  • All of these help us to attain easier handling, better precision, and accuracy while performing operations on numbers with high magnitudes.

Read More: Uncertainty in Measurement