M. 19

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Kelly Cai 4D
Posts: 55
Joined: Sat Jul 20, 2019 12:17 am

M. 19

Postby Kelly Cai 4D » Fri Oct 04, 2019 12:41 pm

A stimulant in coffee and tea is caffeine, a substance of molar mass 194 g/mol. When 0.376 g of caffeine was burned, 0.682 g of carbon dioxide, 0.179 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.

Tiffany_Chen 2K
Posts: 106
Joined: Fri Aug 30, 2019 12:15 am

Re: M. 19

Postby Tiffany_Chen 2K » Fri Oct 04, 2019 2:51 pm

The first step you can take is to convert all of the products into mols, then use the compounds' ratios to find the amount of mols of each element (e.g. there are 2 hydrogens in H2O, so the number of hydrogens would be two times the mols of H2O). Then convert all of the mols into respective grams (except for O, as both CO2 and H2O contains oxygen), and subtract the number of grams of all elements (except O) from the 0.376g of caffeine to find the grams of oxygen produced. Convert the grams of oxygen into mols, and you have a basic empirical formula problem (with mols of O, H, C, and N to work with).

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