<u>Explanation:</u>
Molecular formula is the chemical formula which depicts the actual number of atoms of each element present in the compound.
Empirical formula is the simplest chemical formula which depicts the whole number of atoms of each element present in the compound.
In both the formulas, the nature of atoms remains the same but the number differs.
For Example: The molecular formula of oxalic acid is
but the empirical formula of oxalic acid is 
To calculate the molecular formula, we need to find the valency which is multiplied by each element to get the molecular formula.
The equation used to calculate the valency is:

The empirical mass can be calculated from empirical formula and molar mass must be known.
dim? im not so fluent in this but i did research yesterday
It's pretty easy to balance equations! Basically you want to make sure that the number of each compound is equal on both sides of the arrow.
For example number one is
Fe + H2SO4 -> Fe2(SO4)3 + H2
A 3 in front of H2SO4 because there's a subscript of 3 on the right side.
Then a 3 in front of H2 because of the previous step.
Then add a 2 in front of Fe because of the 2 subscript in Fe2(SO4)3
Then add a 1 in front of Fe2(SO4)3 because you already have an equal number of each element.
<u>2</u>Fe + <u>3</u>H2SO4 -> <u>1</u>Fe2(SO4)3 + <u>3</u>H2
I hope this explanation helps! You should really do your homework because practice is everything when it comes to chemistry. You'll need to know how to do it for exams.
Use a ratio to find out that x/190.2 = 74.5/100
hope this helps