Question

What is the Mass of one Mole of H?

Answer 1

When we are dealing with substances at the macroscopic level we use units like gram or kilogram however for atomic and molecular levels we use the mole concept. Mole concept is used to count particles like electrons, atoms, molecules or ions in the International System of Units (SI).

Complete answer:
Before answering the above question we must understand what actually a mole is-
Mole is defined in number of ways-
It is defined as exactly being equal to $6.022 \times {10^{23}}$ particles (Avogadro number) that can be atoms, molecules or ions.Example-1 mole of $NaCl$ is equal to $6.022 \times {10^{23}}$ $NaCl$ particles or molecules.
A mole is equal to the atomic mass or molecular mass or formula mass (for the ionic compounds) in grams. Example-1 mole of carbon=12g of carbon, 1 mole of carbon dioxide=44g of carbon dioxide etc.
At the STP (Standard temperature pressure) i.e. at 0 °C temperature and 1 atm pressure or at NTP (Normal temperature pressure) i.e. at $25^0C$ temperature and 1 atm pressure ,1 mole of any gas will be equal to 22.4 litre of the gas.
It is given by the formula, $n = \dfrac{N}{{{N_A}}}$ where $n$ the number of moles is, $N$ is the number of molecules or particles and ${N_A}$ is the Avogadro number.
Another formula of mole is mole=given mass/molar mass
An old way of defining mole is-The mass of substance containing the same number of particles as there are atoms in exactly 12 g of 12C.

Hence we can see from all the above definitions that Mass of 1 mole of H will be equal to 1 gram since the atomic mass of the Hydrogen atom is 1 gram, However if you calculate the mass of 1 mole of hydrogen molecule it will be 2 grams.

Note:
The concept of mole is very important to calculate concentration of solution in terms of its Molarity, Molality, Normality, Mole fraction and many other ways. When we deal with any chemical reaction then this concept is highly beneficial thus establishing a standard for reaction stoichiometry. Mole explains the properties of gas and helps distinguish elements and compounds.