Question

Calculate number of neutrons present in 12 × 1025 atoms of oxygen (8O17). (Given NA = 6 × 1023 atoms) (A) 1800 (B) 1600 (C) 1800 NA (D) 3200 NA

Answer 1

Hello Dear.

Here is the answer---

Given ⇒
No. of Atoms of Oxygen = 12 × 10²⁵ atoms.

Atomic Number of Oxygen = 8
Atomic Mass of Oxygen = 17 (Given)

Now, No. of Neutrons = Atomic Mass - Atomic Number
  = 17  - 8
  = 9 neutrons.

∵ 1 Atoms of the Oxygen have 9 Neutrons.
∴ 12 × 10²⁵ atoms of Oxygen have 108 × 10²⁵ neutrons.
 = 10800 × 10²³
 = 1800 × 6 × 10²³
 = 1800 × Nₐ
 = 1800 Nₐ.


Hence Option (C). is correct.


Hope it helps.

Answer 2

Here given, ⁸O₁₇ atom
Means atomic number = 8 and mass number = 17
so, number of neutrons in single ⁸O₁₇ atom = 17 - 8 = 9

Now, number of mole = given number of atoms/Avogadro's number
= 12 × 10²⁵/6 × 10²³
= 200

Now, number of neutrons = number of mole × number of neutrons in single atom × Avogadro's number
= 200 × 9 × Nₐ
= 1800Nₐ
∴ number of neutrons = 1800Nₐ

Hence, answer is option (C)