crazziekid82 Posted October 19, 2008 Share Posted October 19, 2008 hello everyone i need help on a question, i have part of it done adn its correct but to get the rest it not working, this is what i have so far Propane is the major LPG constiturnt, assuming that a 17.60g sample is all propane calculate A) number of propane molecules B) number of carbon atoms C)number of hydrogen atoms propane= C3H8 A) M(c3h8)=44.09gmol-1 n=m/M = 17.09/44.09 =0.40 moles of propane n=N/6.02x10(23) N=0.40x 6.02x10(23) = 2.408x 10(23) B) n©=N/6.02x10(23) = 12.01x 6.02x10(23) = 7.23x10(24) .. the answer says 7.22x10(23) which im not sure what i am doing wrong and i can not get the correct answer for hydrogen, final answer is 1.93 x 10(24) please help with the working out. Link to comment Share on other sites More sharing options...
Klaynos Posted October 19, 2008 Share Posted October 19, 2008 I think you're over thinking it. How many atoms are there per molecule? Then just times that by the number of molecules. Link to comment Share on other sites More sharing options...
insane_alien Posted October 19, 2008 Share Posted October 19, 2008 why have you used 17.09g as the mass of propane and not 17.60g like the question says? and the errors you are getting look like simple rounding errors, try using more significant figures. Link to comment Share on other sites More sharing options...
Imaginer1 Posted October 19, 2008 Share Posted October 19, 2008 I agree with insane alien- and I'm pretty sure C3H8 would be carbon three atoms, hydrogen eight atoms. I don't really see those numbers. P.S. I could be wrong. I'm eleven. I just am more advanced than most Link to comment Share on other sites More sharing options...
insane_alien Posted October 19, 2008 Share Posted October 19, 2008 carbon 3? thats an impossible isotope. what you should have got from that was, 3 carbon atoms and 8 hydrogen atoms. Link to comment Share on other sites More sharing options...
Imaginer1 Posted October 19, 2008 Share Posted October 19, 2008 DONT BLAME ME IM ELEVEN! (runs away) Link to comment Share on other sites More sharing options...
insane_alien Posted October 19, 2008 Share Posted October 19, 2008 dude, chill, i wasn't blaming anyone. just correcting a little mistake. Link to comment Share on other sites More sharing options...
crazziekid82 Posted November 6, 2008 Author Share Posted November 6, 2008 why have you used 17.09g as the mass of propane and not 17.60g like the question says? that was a typing error the answer is still the same. Link to comment Share on other sites More sharing options...
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