Question

Calculate the molar mass of nitric acid $(HN{O_3})$.

Answer 1

Hint : Molar mass of molecules is also called molecular weight . Its unit is gram per mole. We can calculate molar mass of molecule with the help of following rules;
First of all we have to find out atomic masses of individual elements from periodic tables.
Then we have to count the number of atoms which means how many atoms there are for each element.At last we can find out the molar mass of an atom by adding the atomic masses of each atom.

Complete answer:
> We will sum all the atomic masses of each element present in nitric acid. So we know that nitric acid is made up of one hydrogen atom, one nitrogen atom and three oxygen atoms.We know the atomic masses of these elements from periodic table that is given below;
- Atomic mass of hydrogen atom $ = 1.007$ gram per mole
- Atomic mass of nitrogen atom $ = 14.007$ gram per mole
- Atomic mass of oxygen atom = $ = 15.999$ gram per mole
So now we will calculate molecular weight or molar mass of nitric acid with the help of the rules mention in the hint ;
Molar mass of nitric acid $(HN{O_3})$ =atomic mass of hydrogen + atomic mass of nitrogen $ + 3 \times $ atomic mass of oxygen .
Molar mass of nitric acid $(HN{O_3})$$ = 1.007 + 14.007 + 3 \times 15.999$
$ = 63.0144$ gram per mole
So the molar mass of nitric acid is $63.0144$ gram per mole.

Note : Hence in this problem we have found out the molar mass of nitric acid by summation of atomic weight of each constituent atom . We should always remember to multiply the number to the atomic weight by how many times that element is present in the molecule as we have multiplied three to the atomic weight to oxygen .