Determining the Chemical Formula

[SFNUser]

How would I do the following question? Thanks!

[Cap'n Refsmmat]

First things first: you need to figure out how many grams of hydrogen are in 1.21 grams of water. This'll tell you how much hydrogen was in the reactant. The remaining mass of the reactant would have to be carbon (because that's what you usually get in combustion reactions). The ratio of hydrogen to carbon in the reactant gives you the coefficients on the chemical equation, and from there you just compare with the molar mass given in the problem. (You may find that what you have has, say, half the molar mass -- then just double the coefficients.)

 

That's all there is to it.

[hermanntrude]

capn, what's come over you? This should be in homework help.

 

Thread moved

[insane_alien]

Capn, never assume its a hydrocarbon. it could be anything until proven otherwise. assuming is a bad habit to get into. in fact, doing a quick back of the hand calculation, it is impossible for it to be carbon as you would need 2/3 of a carbon atom.

 

when you have the moles of hydrogen, work out how many are in the molecule. the go through the elements and find which one fits.

 

Additional, just worked it out, the formula will seem wrong but its actually a molecule and it has a whole number of atoms.

 

Further additional: actually, there are multiple compounds it could be i'd need to know the other product.

 

Okay, i'd go with the more plausible sounding one. meaning the one you've probably seen before.

Edited September 23, 2008 by insane_alien