## Calculating Empirical Formula with Given Amounts of Each Element

Wilson 2E
Posts: 100
Joined: Sat Aug 17, 2019 12:18 am

### Calculating Empirical Formula with Given Amounts of Each Element

When calculating the empirical formula of a compound and the masses of each element are given, is it necessary to convert the amount of each into a percentage of the actual mass then use the % out of 100g to find the mol ratio, or can you just go from the amounts given to the number of moles of each without calculating Mass Percentage Composition?

Chem_Mod
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Joined: Thu Aug 04, 2011 1:53 pm
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### Re: Calculating Empirical Formula with Given Amounts of Each Element

Your method is acceptable. Keep in mind that when using mass %, you can easily double check that all of the mass of the sample is accounted for. When you convert mass straight to moles, just make sure that all masses given add up to the total sample mass.

Joseph Saba
Posts: 154
Joined: Thu Jul 11, 2019 12:16 am

### Re: Calculating Empirical Formula with Given Amounts of Each Element

Personally, I like using the 100 g method because if there is such a question that says " there is 40%C, 10%O, 20%H, and an unknown amount of a 4th element, it makes it way easier to go from there inorder to calculate the empirical formula.

KarineKim2L
Posts: 100
Joined: Fri Aug 30, 2019 12:16 am

### Re: Calculating Empirical Formula with Given Amounts of Each Element

No, you do not need to convert the masses of each into percentages when masses are given, unless it asks for mass percent.

abby hyman
Posts: 54
Joined: Thu Jul 25, 2019 12:16 am

### Re: Calculating Empirical Formula with Given Amounts of Each Element

Joseph Saba wrote:Personally, I like using the 100 g method because if there is such a question that says " there is 40%C, 10%O, 20%H, and an unknown amount of a 4th element, it makes it way easier to go from there inorder to calculate the empirical formula.

I agree with this, the 100 g method is the easiest because you are able easily convert the percentages into grams.

Nyari Muchaka_Discussion 4A
Posts: 53
Joined: Thu Sep 19, 2019 12:17 am

### Re: Calculating Empirical Formula with Given Amounts of Each Element

No, you do not have to, the 100g method just makes it easier to check the work and execute the problem.

zfinn
Posts: 106
Joined: Fri Aug 30, 2019 12:16 am

### Re: Calculating Empirical Formula with Given Amounts of Each Element

If the masses are already given I usually just convert to moles and go from there since it eliminates the extra steps of converting into percentages!

Charlotte Coplon 1K
Posts: 5
Joined: Thu Jul 11, 2019 12:15 am

### Re: Calculating Empirical Formula with Given Amounts of Each Element

I don't think that you need to use the 100g method but I agree with the above responses that it simplifies the values in the exercise. Say you had an exercise such as F11, where the amount of Oxygen is not stated. Using the 100g method makes it a lot easier to calculate the missing mass of oxygen. With 100g you get 31.91gK, 28.93gCl and (100-60.84)g O. However, the 100g method comes in handy when the masses are not explicit in the exercise, but you need to find the mass percentage composition.