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### Mass Percent Composition

Posted: Mon Oct 08, 2018 6:17 pm
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?

### Re: Mass Percent Composition

Posted: Mon Oct 08, 2018 6:29 pm
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.

### Re: Mass Percent Composition

Posted: Mon Oct 08, 2018 7:07 pm
These problems should always add up to 100%. If not, it might be a trick question or you are mis calculating.

### Re: Mass Percent Composition

Posted: Mon Oct 08, 2018 8:24 pm
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.

### Re: Mass Percent Composition

Posted: Mon Oct 08, 2018 11:42 pm
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%.

### Re: Mass Percent Composition

Posted: Fri Oct 12, 2018 3:19 pm
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%.

### Re: Mass Percent Composition

Posted: Sun Dec 09, 2018 10:18 am
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.

### Re: Mass Percent Composition

Posted: Sun Dec 09, 2018 10:50 am
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.