HW1 M19

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Jeremiah Hutauruk
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HW1 M19

Postby Jeremiah Hutauruk » Sun Oct 07, 2018 5:04 pm

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."

Please and thank you.

Chem_Mod
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Re: HW1 M19

Postby Chem_Mod » Sun Oct 07, 2018 7:45 pm

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
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Re: HW1 M19

Postby Nicolette_Canlian_2L » Tue Oct 09, 2018 5:08 pm

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
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Re: HW1 M19

Postby Sarah Bui 2L » Thu Oct 11, 2018 11:28 pm

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.


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