Question

# Calculate the molar mass of the following substancesA.Ethyne, C$_2$H$_2$B.Sulphur molecule, S$_8$C.Phosphorus molecule, P$_4$ (Atomic mass of phosphorus = 31)D.Hydrochloric acid, HClE.Nitric acid, HNO$_3$

Hint: The molar mass of molecules is defined as the summation of atomic masses of all the atoms present in a molecule. Its unit is represented in the term of grams. By knowing the atomic masses of elements, the molar mass can be determined.

-The first part (A) is Ethyne, the chemical formula is C$_2$H$_2$, we can see that it consists of carbon, and hydrogen. The atomic mass of carbon is 12, and hydrogen is 1. So, the molar mass of ethyne, 2$\times$12 + 2$\times$1 = 26 g.
-The second part (B) is sulphur molecule S$_8$, atomic mass of sulphur is 32. Thus, the molar mass of the sulphur molecule, 8$\times$32 = 256 g.
-The third part (C) is phosphorus molecule, atomic mass of phosphorus is 31. Thus, the molar mass of phosphorus molecule P$_4$, 4$\times$31= 124 g
-The fifth part (E) is nitric acid (HNO$_3$), the atomic mass of H is 1, nitrogen is 14, and oxygen is 16. Thus, the molar mass of nitric acid, 1+14+3 $\times$ 16 = 63 g
The significance of atomic mass comes in solving the stoichiometric calculations and mole concept in chemistry. The unit of molar mass is g/mol. It acts as a bridge in calculating the number of moles because it is not possible to measure the number of moles directly. It should also be noted that the value of Avogadro’s number is $6.022\text{x1}{{\text{0}}^{23}}$$mo{{l}^{-1}}$ and is expressed as ${{N}_{A}}$. Also, The molecular weight is equal to the mass of one mole of the substance.