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Some Basic Concepts of Chemistry question

2025 · 3 Apr · Shift 1 · Q14
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Some Basic Concepts of Chemistry question

2025 · 3 Apr · Shift 1 · Q14

JEE MainChemistrySome Basic Concepts of ChemistryMCQ+4 / −1
Among 10−9 g10^{-9} \mathrm{~g}10−9 g(each) of the following elements, which one will have the highest number of atoms? Element: Pb,Po,Pr\mathrm{Pb}, \mathrm{Po}, \mathrm{Pr}Pb,Po,Pr and Pt
  1. A
    Pr
  2. B
    Pt
  3. C
    Po
  4. D
    Pb
View written solutionFree

Correct answer: A

  1. Idea used

For a fixed mass, the number of atoms is

N=mMNAN = \frac{m}{M}N_AN=Mm​NA​

where:

  • mmm = given mass,
  • MMM = molar mass (atomic mass),
  • NAN_ANA​ = Avogadro's number.

Since mmm is the same for all elements, the element with the smallest molar mass will have the largest number of atoms.

  1. Compare atomic masses

Approximate atomic masses:

  • Pb≈207\mathrm{Pb} \approx 207Pb≈207
  • Po≈209\mathrm{Po} \approx 209Po≈209
  • Pr≈141\mathrm{Pr} \approx 141Pr≈141
  • Pt≈195\mathrm{Pt} \approx 195Pt≈195

Among these, the smallest atomic mass is for Praseodymium, Pr\mathrm{Pr}Pr.

  1. Conclusion

Therefore, among 10−9 g10^{-9}\,\text{g}10−9g each of the given elements, Pr will have the highest number of atoms.

  1. Option check
  • A: Pr ✅
  • B: Pt ❌
  • C: Po ❌
  • D: Pb ❌

So the correct option is:

A: Pr\boxed{\text{A: Pr}}A: Pr​

  1. Comparison with stored answer

Stored correct answer: A

My derived answer: A

They match.

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