Question

Number of neutrons present in 1.7 grams of ammonia is:
(A) ${N_A}$
(B) $\frac{{{N_A}}}{{10}} \times 4$
(C) $\frac{{{N_A}}}{{10}} \times 7$
(D) ${N_A} \times 10 \times 7$

Answer 1

Hint: In order to answer this question you must recall the mole concept in which you have done conversions regarding the number of moles, number of atoms, number of electrons, protons, and neutrons in a sample of given weight. Firstly, find the number of moles of the given sample and use the Avogadro number and the unitary method to find the number of neutrons and then you will get your answers.

Complete step-by-step solution:Step 1: In this step we will find the number of moles of the given sample:
Number of moles of a sample = $\frac{{Given\,Weight}}{{Molecular\,Weight}}$
 Number of moles in 1.7 grams of Ammonia $(N{H_3})$ = $\frac{{1.7}}{{17}}\, = \,\,0.1\,$mole
Step 2: In this step we will find the number of atoms in 0.1 mole of Ammonia:
Number of atoms in 0.1 mole of Ammonia = $0.1 \times {N_A}\, = \,$ $\frac{{{N_A}}}{{10}}$
Here ${N_A}$ is the Avogadro Number.
Since we know that, 1 mole of Ammonia contains: 7 + 3*0 = 7 neutrons. (because Hydrogen do not contain proton)
Step 3: In this step we will find the number of neutrons in 0.1 mole of Ammonia:
Number of neutrons in 0.1 mole of Ammonia = $\frac{{{N_A}}}{{10}} \times 7$
Hence, $\frac{{{N_A}}}{{10}} \times 7$ is the required answer.

Therefore, option (C) is the correct answer.

Note:The number is popularly known as the Avogadro constant and is often denoted by the symbol. The neutron is one of the two constituent parts of an atomic nucleus. The neutron can be treated as a proton that has lost its electrical charge. It is also a very small particle whose radius is equivalent to one millionth of a billionth of a metre, composed of even smaller particles known as quarks.