I want to know how to find molecular mass and atomic mass .
If atomic mass of an element is having isotopes.
Your Sincerely
ABHYODAYA
I want to know how to find molecular mass and atomic mass .
If atomic mass of an element is having isotopes.
Your Sincerely
ABHYODAYA
The atomic weight of an element depends on the abundance of its isotopes. If you know the mass of the isotopes and the fractional abundance of the isotopes, you can calculate the element's atomic weight. The atomic weight is calculated by adding the mass of each isotope multiplied by its fractional abundance. For example, for an element with 2 isotopes:
atomic weight = massa x fracta + massb x fractb
If there were three isotopes, you would add a 'c' entry. If there were four isotopes, you'd add a 'd', etc. Atomic Weight Calculation Example If chlorine has two naturally-occurring isotopes where:
Cl-35 mass is 34.968852 and fract is 0.7577
Cl-37 mass is 36.965303 and fract is 0.2423
atomic weight = massa x fracta + massb x fracb
atomic weight = 34.968852 x 0.7577 + 36.965303 x 0.2423
atomic weight = 26.496 amu + 8.9566 amu
atomic weight = 35.45 amu
Calculating the Molar Mass of an Element
1) Understand molar mass. Molar mass is the mass (in grams) of one mole of a substance. Using the atomic mass of an element and multiplying it by the conversion factor grams per mole (g/mol), you can calculate the molar mass of that element.
2) Find the relative atomic mass of the element. An element's relative atomic mass is the average mass, in atomic units, of a sample of all its isotopes.This information can be found on the periodic table of elements. Locate the element and find the number underneath the symbol for the element. It will not be a whole number, but will have decimals.
- For example, for hydrogen, the relative atomic mass is 1.007; for carbon, it is 12.0107; for oxygen, it is 15.9994; and for chlorine, it is 35.453.
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- 3) Multiply the relative atomic mass by the molar mass constant. This is defined as 0.001 kilogram per mole, or 1 gram per mole. This converts atomic units to grams per mole, making the molar mass of hydrogen 1.007 grams per mole, of carbon 12.0107 grams per mole, of oxygen 15.9994 grams per mole, and of chlorine 35.453 grams per mole.
- Some elements are only found in molecules of 2 atoms or more. This means that if you want to find the molar mass of elements that are composed of 2 atoms, such as hydrogen, oxygen, and chlorine, then you'll have to find their relative atomic masses. Multiply them by the molar mass constant, and then multiply the result by 2.
- For H2: 1.007 x 2 = 2.014 grams per mole; for O2: 15.9994 x 2 = 31.9988 grams per mole; and for Cl2: 35.453 x 2 = 70.096 grams per mole.
- The mnemonic HONClBrIF can help you remember which elements are only found in molecules of 2 atoms. This mnemonic stands for hydrogen, oxygen, nitrogen, chlorine, bromine, iodine, and fluorine.
The atomic weight of an element depends on the abundance of its isotopes. If you know the mass of the isotopes and the fractional abundance of the isotopes, you can calculate the element's atomic weight. The atomic weight is calculated by adding the mass of each isotope multiplied by its fractional abundance. For example, for an element with 2 isotopes:
atomic weight = massa x fracta + massb x fractb
If there were three isotopes, you would add a 'c' entry. If there were four isotopes, you'd add a 'd', etc. Atomic Weight Calculation ExampleIf chlorine has two naturally-occurring isotopes where:
Cl-35 mass is 34.968852 and fract is 0.7577
Cl-37 mass is 36.965303 and fract is 0.2423
atomic weight = massa x fracta + massb x fracb
atomic weight = 34.968852 x 0.7577 + 36.965303 x 0.2423
atomic weight = 26.496 amu + 8.9566 amu
atomic weight = 35.45 amu
Calculating the Molar Mass of an Element
1) Understand molar mass. Molar mass is the mass (in grams) of one mole of a substance. Using the atomic mass of an element and multiplying it by the conversion factor grams per mole (g/mol), you can calculate the molar mass of that element.
2) Find the relative atomic mass of the element. An element's relative atomic mass is the average mass, in atomic units, of a sample of all its isotopes.This information can be found on the periodic table of elements. Locate the element and find the number underneath the symbol for the element. It will not be a whole number, but will have decimals.
- For example, for hydrogen, the relative atomic mass is 1.007; for carbon, it is 12.0107; for oxygen, it is 15.9994; and for chlorine, it is 35.453.
- 3) Multiply the relative atomic mass by the molar mass constant. This is defined as 0.001 kilogram per mole, or 1 gram per mole. This converts atomic units to grams per mole, making the molar mass of hydrogen 1.007 grams per mole, of carbon 12.0107 grams per mole, of oxygen 15.9994 grams per mole, and of chlorine 35.453 grams per mole.
- Some elements are only found in molecules of 2 atoms or more. This means that if you want to find the molar mass of elements that are composed of 2 atoms, such as hydrogen, oxygen, and chlorine, then you'll have to find their relative atomic masses. Multiply them by the molar mass constant, and then multiply the result by 2.
- For H2: 1.007 x 2 = 2.014 grams per mole; for O2: 15.9994 x 2 = 31.9988 grams per mole; and for Cl2: 35.453 x 2 = 70.096 grams per mole.
- The mnemonic HONClBrIF can help you remember which elements are only found in molecules of 2 atoms. This mnemonic stands for hydrogen, oxygen, nitrogen, chlorine, bromine, iodine, and fluorine.
