Question

Number of neutrons present in 1.7 g of ammonia
is -
(1) N
(2) Ng/10 x4
(3) (N/10) Ⓡ7 (4) N, X10 x7​

Answer 1

In one atom of ammonia,

Number of Electrons = 10

Number of Protons = 10

Number of Neutrons = Mass Number - Atomic Number

= 17 - 10

= 7 Neutrons.

Given---

Mass of Ammonia = 1.7 grams.

Molecular mass of Ammonia = 17 grams.

Number of Atoms = (Mass/Molecular mass) × Avogadro's Number(NA)

= (1.7/17) × Avogadro's Number

= 0.1 × Avogadro's Number

= 0.1 Na

∵ one atom of Ammonia contains 7 Neutrons.

∴, 0.1 Na ---------------------------------- 7 × 0.1 Na

= 0.7 Na

= 0.7 × Na

Since Na = 6.022 × 10²³

Thus, Number of Neutrons = 0.7 × 6.022 × 10²³

= 4.2154 × 10²³ Neutrons.