Question

how to calculate molar mass and mass% ?

Answer 1

hey,
molar mass is the sum of total mass (in grams) of all the atoms that make up the molecule.
now, how to calculate it?
firstly, you have to find the no. of each type of atoms in a compound.
secondly, multiply the atomic weight of each compound of each element by the no. of atoms of that compound present in the compound
and finally, add it all and yes, don't forget to put the unit ie.grams/mole.
let us take an example:-
Na₂CO₃
2×23 + 1×12 + 3×16=106 g/mol.

MASS PERCENTAGE OF A SOLUTION:-

mass percent is expressed as the grams of solute divided by the grams of solution, then multiplied by 100 to get a percentage.
mas percent=mass of solute/mass of solution ×100
you should know the mass of solute and mass of solution=mass of solute+mass of solvent.
hope it helps you :)

Answer 2

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Molar mass

As the molecules are made of atoms, they also have their own mass. The mass of the molecule of an element or compound is measured in the C-12 scale and hence called relative molecular mass.The Relative Molecular Mass of a molecule is the ratio between the mass of one molecule of the substance to 112th mass of an atom of Carbon -12.Relative Molecular Mass is only a ratio. So, it has no unit. If the molecular mass of a com-

Let's take an example "Ca3 (PO4)2"

meathod to calculate:-

Atomic masses of:-

Ca = 40

P = 30

O = 16.

Gram molar mass of Ca3 (PO4)2=

♠40 × 3) + [30 + (16 × 4)] × 2

♠120 + (94 × 2)

♠120 + 188

Gram molar mass of Ca3(PO4)2 = 308 g

Mass%

So for, we were dealing with the number of entities present in a given substance. But many times, the information regarding the percentage of a particular element present in a compound is required.The percentage composition of a compound represents the mass of each element present in 100 g of the compound.Let us understand the percentage of the compound.Let us understand the percentage composition of oxygen and hydrogen by taking the example of H2O.

For example:-

Mass % of an element

= mass of that element in the compound × 100 molar mass of the compound

Now,

♠molar mass of H2O = 2(1) + 16= 18g

♠Mass % of hydrogen = 2/18× 100= 11.11 %

♠Mass % of oxygen = 16/18× 100= 88.89 %

This percentage composition is useful to determine the empirical formula and molecular formula.

Hope it helps

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