Question

In $6.72\,g$ of${N_2}{H_4}$, how many?
A.How many ${N_2}{H_4}$ molecules are present?
B.How many $N$ atoms are present?
C.How many protons are present?

Answer 1

Hydrazine is an inorganic compound having the chemical formula of ${N_2}{H_4}$. A mole is defined as $6.02214076 \times {10^{23}}$ of a chemical unit in the terms of ions, atoms, molecules, etc.
$1\,mole\, = \,6.022\, \times \,{10^{23}}\,atoms$
Therefore, for $1$ atom will be;
$1\,atom\, = \,\dfrac{1}{{6.022\, \times \,{{10}^{23}}}}\,moles$
So, the answer will be;
$1\,atom\, = 1.66\, \times \,{10^{ - 24}}\,moles$

Complete step-by-step answer: First, we need to find how many ${N_2}{H_4}$ molecules are present?
Let’s observe the given values;
Here, we have {N_2}{H_4}$$$$ = \,6.72\,g
To calculate the number of moles;
Let’s use the equation;
Number of moles, $n\, = \,\dfrac{{mass}}{{molecular\,mass}}$
The given mass of hydrazine $({N_2}{H_4})\, = \,6.72\,g$
The molecular mass of hydrazine $({N_2}{H_4})\,$;
$= \,14\, \times \,2\, + \,1\, \times \,4$
$= \,32{\text{ }}g/mol$
Substitute the values in above equation,
$n\, = \,\dfrac{{6.72\,g}}{{32\,g/mol}}$

So, the number of moles will be;
$n\, = \,0.21\,moles$
We have to multiply with the Avogadro’s number to get the $({N_2}{H_4})\,$ molecules.
Now, let’s calculate the number of molecules present in $6.72\,g$ of $({N_2}{H_4})\,$
$= \,0.21\, \times \,6.023\, \times \,{10^{23}}$
$= \,1.2648\, \times \,{10^{23}}$ molecules
So, the answer obtained will be, $1.2648\, \times \,{10^{23}}$ molecules are present in $6.72\,g$ of $({N_2}{H_4})\,$ .
Secondly, we need to find that how many $N$ atoms are present;
So, for that we must know that there are two atoms of nitrogen participating for every molecule of hydrazine;
$= \,1.2648\, \times \,{10^{23}}\, \times \,2$
$= \,2.52\, \times \,{10^{23}}$ atoms of nitrogen.
Thirdly, we need to find how many protons are present;
We know that the atomic number will be equal to the number of electrons and the electrons are equal to the number of protons. So, we have $7$ protons of nitrogen because the nitrogen’s atomic number is $7$ and $1$ protons of hydrogen because the atomic number is $1$ .
But we need to calculate the atoms of hydrogen so that the calculation can be easy;
So, for that we must know that there are four atoms of hydrogen participating for every molecule of hydrazine;
$= \,1.2648\, \times \,{10^{23}}\, \times \,4$
$= \,5.05\, \times \,{10^{23}}$ atoms of hydrogen.
Now, let’s calculate the number of protons;
So, the total number of protons will be;
$= \,7\, \times \,2.52\, \times \,{10^{23}}\, + \,1\, \times \,5.05\, \times \,{10^{23}}$
$= \,22.69\, \times \,{10^{23}}$ protons are present.

Note: A mole is a unit measurement for the amount of substance in the international system of units i.e., SI unit. A mole of a particle or a mole of a substance is defined as $6.02214076 \times {10^{23}}$ of a chemical unit, that can be ions, atoms, molecules, etc. Originally it was defined as the number of atoms in $12{\text{ }}g$ of carbon-12.