Mass Percent Composition

[Madeline Louie 1I]

If you are given the amount of an element in grams when asked to find the empirical or molecular formula, is it necessary to convert it to its mass percent composition using its mass and the total mass, or can you simply convert the grams to moles and proceed as normal. Would you get the same answer either way you do it? Sorry if this is kind of confusing, but I appreciate the help in advance!

[kateraelDis1L]

Whenever it says like "the total mass of this sample (or compound) is [censored]" then you need to take the individual grams and find mass percent composition.

[Ashley Ko 3I]

Hi! If given mass percent composition, then you should convert the percentages to grams and then calculate the mol of each element to find the empirical/molecular formulas. However, if given the mass of each element (not percent mass composition), you can convert directly to mol and then find the empirical/molecular formula. Hope this helps!

Also, you get the same answer whether you convert from grams to mols directly or convert the masses so that they are out of 100 g (this is for when the mass of each element is given but not percent mass composition).

[Alessia Renna 1D]

If you are given the grams of each element in the compound, you should find the percent mass composition first and then convert to grams (assuming a total of 100 g) and then convert to moles!