Question

Number of hydrogen atoms in 9.6g ${{N}_{3}}H$ ?

Answer 1

Hint: The number of atoms in a compound will be calculated by the weight of the sample, its atomic mass from the periodic table, and a constant needed Avogadro’s number. A conventional method of expressing the amount of substance by using the mole concept.

Complete answer:
the number of moles in a sample of an element or compound can be calculated by the ratio of the total mass of the sample to the molar mass or the element or compound as described by the following formula,
Number of moles = (mass of the sample)/(molar mass)
The following steps to calculate the number of hydrogen atoms in 9.6g ${{N}_{3}}H$
Step-1: Find the molar mass of the formula
The molar mass of ${{N}_{3}}H$ = 43 grams/mol
A mole of H atoms = $6.023\times {{10}^{23}}$ H atoms
A mole of N atoms = $6.023\times {{10}^{23}}$ N atoms
1 mole of ${{N}_{3}}H$ atoms = $6.023\times {{10}^{23}}$ of ${{N}_{3}}H $ atoms
Step-2: Find the number of moles:
$9.6g{{N}_{3}}H\times \dfrac{1\text{ }mole{{N}_{3}}H}{43g/mol{{N}_{3}}H}$ = 0.223 moles of ${{N}_{3}}H$
Step-3: convert moles into atoms using Avogadro’s number:
The number of atoms in the given molecule may be calculated by Avogadro’s number with the help of amount moles known in step -2
$\text{0}\text{.223moles }of\text{ }{{N}_{3}}H\times \dfrac{6.023\times {{10}^{23}}}{1\text{ }mole\text{ }of\text{ }{{N}_{3}}H}$ = $1.343\times {{10}^{23}}$ atoms of ${{N}_{3}}H$

Hence, $1.343\times {{10}^{23}}$ atoms of hydrogen in 9.6g of ${{N}_{3}}H$.

Note:
Sometimes the number of moles of its constituent elements may not always be equal to the number of moles of the molecule. The total number of molecules or atoms in a sample molecule can be calculated by the number of moles multiplying with Avogadro’s number.