Molecular Mass Definition Class 11

Category: Chemistry, Class 11, Some basic concepts of chemistry labeled with: atomic mass, fractional abundance, grams atomic mass, grams molecular weight, molecular weight, one unit of atomic mass “molecular weight”. Dictionary, Merriam-Webster, Retrieved 11 October 2022. Therefore, carbon is used to determine atomic masses. The molecular weight of an element is defined as the sum of the masses of the elements present in the molecule. Molecular weight is obtained by multiplying the atomic mass of an element by the number of atoms in the molecule and then adding the masses of all the elements in the molecule. Let`s take an example: carbon dioxide. The molecular weight of carbon dioxide (begin{array}{l}CO_2end{array} ) = atomic mass of carbon + 2 × (atomic mass of oxygen) = 12.011 u + 2 × (16.00 u) = 44.011 u In addition to the molecular weight, we also have the formula mass. This mass is used for compounds that do not have discrete molecules as components. For example, in NaCl, a Na+ is surrounded by six Cl- and vice versa. Molecular weight has no meaning in such cases, since the molecule exists as a unit. Therefore, in these cases, we use the mass formula to calculate the mass of the molecule.

The atomic mass of an element is the frequency at which an atom of that element is heavier than a carbon atom taken as 12. The molecular weight of a substance is the frequency at which the molecule of the substance is heavier than one-twelfth of the mass of a carbon-12 atom. For example: molecular weight of oxygen = 32u grams molecular weight of oxygen = 32 g The atomic mass of an element, expressed in grams, is called atomic mass in grams. One atomic mass unit is one-twelfth the mass of an atom of the carbon-12 isotope. The atomic mass of an element is the average relative mass of its atoms relative to a carbon-12 atom, which is considered 12. Initially, the atomic masses of all elements were obtained by comparison with the mass of hydrogen as 1, but this resulted in atomic masses of most elements as broken. Atoms are very small particles and therefore their masses are extremely small. Nowadays, the spectroscopy method is used to accurately determine the mass of an atom. But in the nineteenth century, scientists used the concept of relative atomic mass to find the mass of an atom. Elemental hydrogen was considered the norm and its mass was assumed to be 1 (without units). Other elements were compared to the atomic mass of hydrogen and their relative masses were obtained.

The current scenario is different and now the standard used for atomic weights is carbon-12, an isotope of carbon. This standardization has prevailed throughout the world. The mass of C-12 is 12 atomic mass units and all elements are assigned their respective masses according to this standard. A unit atomic mass is equal to (begin{array}{l}frac{1}{12^{th}}end{array} ) of the mass of a carbon-12 atom. The word amu, which is atomic mass unit, has been replaced by “u”, which means uniform mass. If the elements have isotopes, then the atomic mass of the element is the sum of the relative abundance of the element multiplied by the atomic mass of the respective isotopes. Dr. Shilpi Nagpal is a PhD student in chemistry and an experienced tutor who has been teaching students since 2007.

She specializes in science tutoring for students in grades 6 to 12. Ms. Nagpal has a proven track record and her students have consistently scored better and scored better on tests. She is eloquent, knowledgeable and her passion for teaching shines through in her work with students. Thank you Mam for this site for us….. Your email address will not be published. Required fields are marked with * The fractional abundance of an isotope is a fraction of the total number of atoms made up of that particular isotope. Put your understanding of this concept to the test by answering a few MCQs. Click “Start Quiz” to get started! Tq for these solutions It helped me a lot Thank you Visit BYJU`S for all questions related to chemistry and study material Thank you, madam. This article was really helpful. Send your best wishes and gratitude to Bhopal. Select the correct answer and click the “Finish” button, check your score and answers at the end of the quiz.