Calculate the molar mass

Answer 1

Example for sodium chloride, NaCl:

- search in tables the atomic weights of the constitutive elements, Na and Cl:

Na = 22,989 769 28

Cl = 35,453

- calculate the molar mass:

MNaCl = ANa + ACl = 22,989 769 28 + 35,453 = 57,958 622 382

Answer 2

Molar mass means the mass of 1 mole of a substance in grams.

Here, H2O doesn't have any co-efficient which means that there is only 1 mole of H2O (Water). If it is two moles , then there will be a co-efficient of 2 before H2O and will be written as 2H2O.

Now, we have only 1 mole. The mass of 1 mole of a substance is the same as its molecular weight.

Molecular weight is calculated by adding up the Atomic Mass of each constituent element by the number of the atoms present.

i.e., Atomic mass of H is 1u (approximately) and O is 16 u.

Thus, we get (2x1) + (1x16) = 2+16 = 18 grams (We multiply 2 to 1 as there are TWO atoms of Hydrogen in the compound. Similarly, we multiply 1 to 16 as there is only one atom of Oxygen)

Thus, the molar mass of H2) is 18 grams (approximately).

NOTE: Hydrogen is said to have an atomic mass of 1.008u. But, it is generally takes as 1u as the number is very small.

If the value is taken as 1.008 u, then the molar mass of H2O is 18.02 grams (Done by the same steps as above).

Answer 3

You can use the formuar mass/moles if you have the mass and the moles of that element or you can as well weigh one mole of an element.