How to solve these chemistry questions about moles?

[aero]

1. How to work out the number of particles? Do you have a formula and an example?
2. Are atoms present in sodium oxide?
3. How to calculate molar mass?
4. How to convert mole to mass and mass to mole?

[123654777]

1.
a mole is a unit of measurement.
1 mole of anything = 6.022x10^23 units
this is called avagadros number

So 1 mole atoms = 6.022x10^23 atoms
1 mole molecules = 6.022x10^23 molecules
1 mole eggs = 6.022x10^23 eggs

To work out number of particles (weather atoms, or molecules or formula units) work out the number of moles, and then multiply by avagadros number.

2.
Yes, compounds are made up of atoms bonded together

sodium oxide is Na2O

1 molecule of Na2O contains
2 atoms of Na
And 1 atom of O

To add it to question 1
1 mole of Na2O has 6.022x10^23 molecules of Na2O

But each Na2O has 2 atoms of Na
So number of Na atoms in 1 mole Na2O = (2 x 6.022x10^23) Na atoms = 1.2044x10^24 Na atoms

Each Na2O has 1 atom of O
so 1 mole Na2O has 1 mole O atoms = 6.022x10^23 atoms of O

Each Na2O has 3 total atoms (2 O + 1 Na)
So total number of atoms in 1 mole Na2O = 3 moles
So number atoms = 3 x 6.022x10^23 atoms
= 1.8066x10^24 atoms in 1 mole Na2O

3.
molar mass of a compound = sum of atomic mass of every atom in the compound in grams

eg CH4 = 12.01 + (4 x 1.008) =  16.042 g/mol

4.
moles = mass / molar mass

the equation can be rearranged to solve for mass and molar mass

mass = moles x molar mass
molar mass = mass / moles