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### Empirical Formula

Posted: Thu Oct 04, 2018 9:52 am
I'm going over the notes from Monday's lecture, and I noticed that in the vitamin c example he did, when trying to find the mass of the elements after finding the mass percentage of each, he used 100g as the sample mass. Will we always do this with these problems, unless we're told otherwise?

### Re: Empirical Formula

Posted: Thu Oct 04, 2018 10:33 am
I was wondering the same thing. When determining the empirical formula, I am pretty sure that we always assume/ imagine that the sample mass is 100 grams as this is the easiest way to convert the mass percentages into the mass (in grams). Can someone confirm if this is true for every problem where we need to determine the empirical formula?

### Re: Empirical Formula

Posted: Thu Oct 04, 2018 11:20 am
When we have percentages for elemental composition, it makes it much easier to determine the grams in the sample (especially if we do not have a sample given), then we can use molar masses to determine the moles and the empirical formula. In essence, it makes it much easier to glean important information (mass samples to convert to moles), but it is not explicitly necessary if you already have such information given. In my opinion it's a very easy and logical way to keep your numbers simple, and to go step by step.

### Re: Empirical Formula

Posted: Thu Oct 04, 2018 11:56 am
Yes, I believe you always assume that the compound has a total mass of 100g simply because it is much easier to solve with this assumption.

### Re: Empirical Formula

Posted: Thu Oct 04, 2018 12:54 pm
technically you can use any mass you choose however 100g is almost always used as it reduces the amount of calculations needed and makes it simpler

### Re: Empirical Formula

Posted: Thu Oct 04, 2018 3:51 pm
You do not need to do it every time, you can use any amount you want for mass to solve for how much the percentage accounts for, however, since percent means a part of ONE HUNDRED, then it is much easier to use 100g as the mass because you would only need to change the percent sign to grams.

### Re: Empirical Formula

Posted: Fri Oct 05, 2018 1:13 am
We just assume that it is 100g unless otherwise stated to make it easier to calculate percentages.