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Gayathri Mani

HS-PS1-3

Molar Mass Study Guide

Mass/molar mass can be defined as the smallest unit of mass of any compound and is the twelfth of one carbon mass- 12 atoms. Read on to find more.

INTRODUCTION

Have you ever wondered what the exact number of molecules present in a football you are playing with or the water you are drinking is? We know by now that atoms or molecules are the smallest units when considering both mass and size. The weight of one sample mole is the molar mass. The molar mass is calculated by adding all the atomic masses of each and every atom in a molecule. How can molar mass be defined then?

WHAT IS MOLAR MASS IN CHEMISTRY?

The molar mass of any substance is defined as the smallest mass unit of that compound with one-twelfth of the mass of one carbon that would be 12 atoms. In any substance, the number of entities present can always be defined as a mole.

Moles Source

WHAT IS THE MOLAR MASS UNIT?

You can take the standard unit to be g mol⁻¹ and the SI one as kg mol⁻¹. The number of atoms that is observed in 12g of 12C isotope is the number of particles you would also observe in 1 mole of the substance. Remember, no matter the substance, the mole of any substance would always contain the same entity number.

A spectrometer was used to measure the mass of carbon-12 atoms, and it was found to be 1.992648x 10⁻³g. The number of entities in one mole is crucial while calculating the mass in chemistry and is known as the Avogadro number, which is 6.02214076 x 10²³.

MASS AND MOLAR MASS FORMULA

It might seem easy to calculate the formula masses of molecules, atoms, and other such compounds; however, finding individual weights of these particles does not serve any useful purpose. They should be expressed at a more macroscopic level, and the bridge between this particulate and the macroscopic level is considered as the molar mass.

                   Molar mass = mass/mole = g/mol

Molar Mass Unit Source

HOW CAN YOU EASILY FIND THE MOLAR MASS FOR DIFFERENT COMPOUNDS?

Let us take an example to understand how to calculate the molar mass of NaCl.

molar mass Source

  • Using the periodic table, find the atomic masses: For each element, you must figure out the atomic mass using the periodic table. For any element, the number that appears on the top left represents atomic mass. The atomic mass of sodium would be 22.98976 g/mol, and that of chlorine would be 35.453 g/mol.
  • Count the number of atoms present in each element: Since there are no subscripts, that means there is only one sodium and one chlorine atom in this compound.
  • Now Find the molar mass: Now that you know the atomic mass and how many atoms of the compound are involved, you can find the molar mass as shown in the example.

CONCLUSION

  • Molar mass can be defined as the smallest unit of mass of any compound and is the twelfth of one carbon mass - 12 atoms.
  • The standard unit is g mol⁻¹ and the SI one as kg mol⁻¹.
  • You can find the molar mass if you know the atomic mass and number of atoms involved in each element.

FAQs

1. Is mass equal to molar mass?

Molar mass is considered to be the same as the formula mass.

2. What is meant by molar mass?

Molar mass can be defined as the smallest unit of mass of any compound and is the twelfth of one carbon mass- 12 atoms.

We hope you enjoyed studying this lesson and learned something cool about Molar Mass! Join our Discord community to get any questions you may have answered and to engage with other students just like you! Don't forget to download our App to experience our fun VR classrooms - we promise, it makes studying much more fun! 😎

SOURCES

  1. Molar Mass: https://byjus.com/chemistry/mole-concept-molar-mass-and-percentage-composition/.Accessed 10th March 2022.
  2. What Is Molar Mass? https://study.com/academy/lesson/what-is-molar-mass-definition-formula-examples.html.Accessed 10th March 2022.