Question

The weight of 4 gram atoms of nitrogen is:
A.56 gm
B.112 gm
C.42 gm
D.28 gm

Answer 1

Hint: To calculate the weight of a 4 gram atom of nitrogen, we should note the question is asking about the weight of nitrogen atom. Nitrogen atoms are single N, whereas molecules of nitrogen are diatomic.

Step by step answer:
First, we should understand a simple concept.
One gram of nitrogen means it has only one atom of nitrogen.
So, four gram atom of nitrogen has four atoms of nitrogen.
We can also represent the number of moles. We can say that one gram of atoms is equal to one mole of nitrogen and in the same way four gram atoms of nitrogen is equal to four moles of nitrogen.
After that we can say that the molar mass of nitrogen is 14 gram per mole.
Now, we can easily calculate the weight of four gram atoms of nitrogen by using mole formula.
\[Number\,of\,moles=\dfrac{weight\,of\,nitrogen}{molar\,mass\,of\,nitrogen}\]
\[\begin{align}
  & 4=\dfrac{weight\,of\,nitrogen}{14} \\
 & weight\,of\,nitrogen=14\times 4=56\,gram \\
\end{align}\]
So, from the above discussion we can say that option A is correct.

Note: We should note that the mass of one mole of a substance is equal to that substance’s molecular weight. For example, the mean molecular weight of water is 18.015 atomic mass units (amu), so one mole of water weighs 18.015 grams. We should note that Avogadro’s number is a very important relationship to remember:
One mole = \[6.022\times {{10}^{23}}~\]atoms, molecules, protons, etc.
We should note that, if we want to convert from moles to atoms, multiply the molar amount by Avogadro’s number and vice versa.