Basic Stoichio with a missing element? Please help :(!?
a compound is composed of element X and hydrogen. Analysis shows the compound to be 80% X by mass with three times as many hydrogen atoms as X atoms per molecule. Which element is element X?
the answer is carbon
- AshleyLv 68 years agoFavorite Answer
XH₃ means a mass of 3. so 3 is 20% of some number. 300/20 = 15, so the whole mass is 15. That means the mass of X is 12. That would be carbon
- Anonymous8 years ago
So your formula is XH3, right?
It's got to be a group 3 or 5 element, because those take 3 bonds. NH3, ammonia, BH3 boron trihydride or AlH3, aluminum trihydride.
N is 14g/mol. H 1g/mol
NH3 is 17g/mol.
14/17 = 0.82 (82% mass) while 3/17 = 0.18 (18% mass)
B 10.8g/mol so BH3 = 13.8g/mol
10.8/13.8 = 78.3% B, 11.7% H
Al 27g/mol so AlH3 30g/mol
27/30 = 90% Al, 10% H
Can't be this one, % too high
Gotta be N or B... which is a choice on your test? Pick that one.
Close enough for govt work! :)
Hope this helps! :)Source(s): http://www.ptable.com/