## Empirical Formulas

10/28/2013

16 Comments

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## Comments

Allison Schweiger
10/11/2012 9:36pm

Why do we assume the mass is 100g if we aren't given a mass?

Rourke
10/14/2012 12:41am

Since the % composition is % mass and the % must equal 100%, we can assume not matter what the mass is: 100g, 200g, 1 kg, the percent of each component won't change. So for simplistic measures we use 100g, though we could just as easily use 1g, 200g, or 1kg.

Laurel Payne
10/12/2012 7:36pm

How do you know how many grams of an element make up a mol of that element (I noticed they were all different)?

Lee Muglia
10/13/2012 4:48pm

To find how many grams, look at the mass of the element of the periodic table and round it to the closest whole number

Rourke
10/14/2012 12:43am

Correct Lee

Lee Muglia
10/13/2012 4:52pm

If you divide the amount of electrons, wouldn't that change the compound because it has a different amount or does it only change if the number of protons change? Also, in the example with CH4, why is the CH4 that cannot be reduced emperical formula while the other two CH4's are still molecular form even though they have been reduced?

Rourke
10/14/2012 12:37am

They would be considered the molecular formulas of CH4.

Bailey Ernst
10/13/2012 10:39pm

Heylee! I think the answer to your second question is that the two forms, C2H8 and C3H12, are still recognized as the molecular formulas (even though they were reduced) because of the fact that they did not start out as CH4. Since the first CH4 did not branch off and was not reduced, it stayed the Empirical Formula.

Bailey Ernst
10/13/2012 10:40pm

I noticed that I did not hit "reply" to Lee's original comment...oops haha

Rourke
10/14/2012 12:42am

Correct

Faith Barzyk
10/14/2012 1:03pm

How do you find out that 1 mol of Oxygen is equal to 16 grams of Oxygen?

Megan Bishop
10/14/2012 3:39pm

I found that one mol of something is equal to its atomic mass. So, i believe that since Oxgen's atomic mass is about 16, there would be 16 grams of Oxygen in one mol?

Ben Evans
10/14/2012 3:37pm

So to figure out the mass of one mol of an element, all you do is double the atomic number? What would happen if it was an isotope? Would this change the mass of the mol?

Krista Wylin
10/14/2012 8:14pm

Is the amount of the element in grams always equal to it's atomic mass on the periodic table? Or does it just work for some of the elements?

Carly Zebelian
10/14/2012 8:39pm

why do you always assume that its 100g how do you know its not something different

Sara Campbell
10/14/2012 8:55pm

On the first page, you wrote 193 grams, but you said 139 grams, but you meant 193, right? Just checking