## HW1 M19

Jeremiah Hutauruk
Posts: 67
Joined: Fri Sep 28, 2018 12:28 am

### HW1 M19

It says "M.19 A stimulant in coffee and tea is caffeine, a substance of molar mass 194 g mol 1. When 0.376 g of caffeine was burned, 0.682 g of carbon dioxide, 0.174 g of water, and 0.110 g of nitrogen were formed. Determine the empirical and molecular formulas of caffeine, and write the equation for its combustion."

Chem_Mod
Posts: 19198
Joined: Thu Aug 04, 2011 1:53 pm
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### Re: HW1 M19

There wasn't much of a question there! I'll give you some hints instead. The problem is telling you grams of products. You know that they could only have come from the caffeine and the oxygen used to combust it. You can use the grams given to determine how many moles of carbon were produced, you know all that came from the caffeine. Same can be said for nitrogen and hydrogen. You need to be able to determine how much of the oxygen produced came from the caffeine, which is the hard part! If you still have trouble, post a more specific question later.

Nicolette_Canlian_2L
Posts: 77
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### Re: HW1 M19

Do we have to first convert the grams of each compound into moles and then find the mass of the individual elements from there?

Sarah Bui 2L
Posts: 61
Joined: Fri Sep 28, 2018 12:29 am

### Re: HW1 M19

Nicolette_Canlian_3G wrote:Do we have to first convert the grams of each compound into moles and then find the mass of the individual elements from there?

Yes, but remember to also look at your stoichiometric coefficients for the ratios to compare to and then find the mass of the individual elements. To find the mass of O subtract 0.376 g of caffeine from the sum of each of the masses found for C, H, and N.