Hey can someone help me with this question:
Draw the stuctural formula of 1,2,3-trimethylbutan-1-ol
the answers have 2 OH's .....dont know if they made a mistake
btw the question is in pg.136 Q8 d in the jacaranda textbook
thanks
That's a pretty weird question already, since that molecule when drawn out should really be named by "pent-" rather than "but-". There are 5 carbons in the longest chain, since there is a methyl group off the end.
Also,
An oxide of iron contains 21.33% oxygen by mass. Find the empirical formula. Ans: Fe(2)O(3)
1 gram of the iron oxide has 0.2133 g of oxygen and 0.7867 g of iron. Divide by their molar masses to reveal:
} = 0.01333\mbox{ mol})
} = 0.01407\mbox{ mol})
Note: the fact we chose "1 gram" makes no difference, because we're interested in the ratio between:
} : \mbox{n(O)})
for the empirical formula, which will be the same regardless of how much grams we worked with to begin with (I arbitrarily chose 1 gram - you could choose 100 if you like).
Anyway:
} : \mbox{n(O)} = 1:1)
(roughly, is good enough)
Hence
is the empirical formula. I disagree with the answers.
A compound X is used in ceramic work in the form of its hemihydrate X..5H(2)O which, when mixed with water, gives a solid dihydride X.2H(2)O. If 2.9g of hemihydrate yeilds 3.44g of dihydride, what is the molar mass of the dihydrate X.2H(2)O Ans, 136
} = \mbox{M(X)} + 0.5(18.0))
} = \mbox{M(X)} + 2(18.0))
Since the
must balance on both sides of the equation
, then they are equimolar:
} = \mbox{n(dihydrate)} = n)
Since
} + 0.5(18.0)} = \frac{3.44}{\mbox{M(X)} + 2(18.0)})
} + 104.4 = 3.44\mbox{M(X)} + 30.96)
} = 73.44)
} = 136\mbox{ gmol}^{-1})
Once again, the answer is
wrong, because we're not done: we want
} = 136 + 2(18.0) = 172\mbox{ gmol}^{-1})
Crap book.
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