Molar mass of hydrogen: heavy and light

The easiest of the chemical elements, an obligatory component of organic substances, is a necessary part of the molecules of life - water - and it's all about hydrogen. The very name of it in Russian is translated by converting parts of the Greek word - "giving birth to water". Hydrogen as a gas is a rather whimsical and dangerous substance (it ignites!). And hydrogen in the atomic form is very active and has reducing properties. Therefore, in the school's chemical problem books, students can be asked to determine what the molar mass of hydrogen is. This question can confound even adult chemists who have forgotten the chemistry.

Specify what is meant

The very concept of "hydrogen" from a logical point of view is ambiguous. It can mean both hydrogen atoms and the corresponding gas existing in the molecular form. In the second case, it is a set of two atoms. Most likely, in the notion of "molar mass of hydrogen" is meant gas, since for individual atoms the concept of atomic mass is more often used . But in a free form, hydrogen can exist, especially with certain physicochemical processes. And the mole of this substance has a mass. Therefore, every time you solve a problem, specify what exactly is meant.

Free atom

If an atom is meant, the molar mass of hydrogen is one gram per mole. It can be converted into kilograms per mole to comply with the requirements of the SI, for this you just need to multiply 1 by 10 to minus the third degree. Although these data will not be exactly accurate, because atomic weights are not fractions, but fractional.

So heavy!

But be careful - if you solve a problem in a physics textbook, you may encounter heavy forms of hydrogen that have a different molar mass. The most common hydrogen is called protium and its mole weighs one gram, but there is also deuterium (2g per mole), and tritium (3g per mole). Deuterium in very small amounts (less than 0.2%) occurs on Earth, and tritium generally does not occur, but it is easy to obtain in nuclear reactions. In the process of solving real problems, physics and chemistry are not delineated, so if you are preparing for a career in the natural sciences, you need to be ready to determine the molar mass of hydrogen in such unusual situations.

Calculations for the molecular form

If the problem means gas, then you will need to multiply the atomic mass of hydrogen by two and assign a unit of r to a mole. Atomic units and grams per mole are equivalent numerically, but the former are used more in physics and discussing the properties of elements, and the latter are used in solving practical problems in chemistry. But even here you can be caught and wondered by the mass of heavy hydrogen. By the way, be careful, sometimes you will not expect multiplication of 2 or 3 in two from you. There are hybrid forms, for example, deuterium with tritium (the molar mass of hydrogen in this case is 2 + 3 = 5), or protium with deuterium (3), or tritium with protium (4). Therefore, reason logically and add, and do not multiply, so as not to make mistakes with heavy molecules.

It is interesting that water, which includes heavy hydrogen, is also called heavy. Problems with its production from heavy hydrogen can cause difficulties and it is for this purpose, it may be necessary to calculate the molar mass of hydrogen in your particular situation.