## Mass Percent Composition

Moderators: Chem_Mod, Chem_Admin

Megan_Ervin_1F
Posts: 78
Joined: Fri Sep 28, 2018 12:18 am

### Mass Percent Composition

For Mass percent composition questions, why doesn't it always add up to 100? What do you do when it doesn't add to 100?

Adam Vuilleumier 2K
Posts: 60
Joined: Fri Sep 28, 2018 12:27 am

### Re: Mass Percent Composition

Mass percent composition problems will always add up to 100% if all the elements in the molecule are listed in the problem. I'm guessing that the reason you aren't getting 100% is round-off error.

harperlacroix1a
Posts: 43
Joined: Fri Sep 28, 2018 12:19 am

### Re: Mass Percent Composition

These problems should always add up to 100%. If not, it might be a trick question or you are mis calculating.

Aleeque Marselian 1A
Posts: 60
Joined: Fri Sep 28, 2018 12:24 am

### Re: Mass Percent Composition

All mass percent composition questions should provide you with information adding up to 100 or should give you a solution that is equal to 100. If not there is either in error in the question or the method used to solve.

Clarissa Cabil 1I
Posts: 66
Joined: Fri Sep 28, 2018 12:19 am

### Re: Mass Percent Composition

For mass percent composition problems, if percentages are given to each element, the elements' percentages should all add up to 100%. However, if the masses, or grams, of each element are given, then the masses of the reactants should be equal to the masses of the products. You then convert the masses by dividing the given mass of each element from the total mass in order to find the mass percentage composition of each element, which should then add up to 100%.

Kyither Min 2K
Posts: 60
Joined: Wed Oct 03, 2018 12:15 am

### Re: Mass Percent Composition

It should add up to 100% since mass can not be created nor destroyed and what mass percent composition is stating is just how much the particular element weighs in the whole compound, or it is a percentage of the total mass and so percentages should always add up to 100%.

uhedlund
Posts: 38
Joined: Wed Nov 15, 2017 3:03 am

### Re: Mass Percent Composition

Mass percent should always add up to 100%. If you are given non-Oxygen elements and they do not add up to 100, then Oxygen is likely the remaining element and can be used to fill the deficit.

davidryan3f
Posts: 63
Joined: Fri Sep 28, 2018 12:23 am

### Re: Mass Percent Composition

If it does not add up to 100%, then the question is incorrect. The elements that are apart of the compound have to add up to 100% or else there is a missing element.

Return to “Empirical & Molecular Formulas”

### Who is online

Users browsing this forum: No registered users and 3 guests