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Physical Chemistry

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26 Oct 2006 16:24:39 IST

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formula for a compound on percentage weight

None

two elements A(at. wt.=75) and B (at. wt=16) combines to give a compound having 75.8 % of A,wht is the formula of compound ?

i have found the moles of both A and B as 1 and 1.5 and then converted them to whole no. as 2 and 3 , so the formula according to me should be A subscript 3 and B subscript 2 becuase we know the formula for a compound (M subs.x N subs.y)= x moles of N=y moles of M but in the book answer is given as A subs.2 and B subs.3 please tell the correct answer and why ? help as soon as possible.

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Comments (3)

arun-rashi

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Joined: 19 Oct 2006

Posts: 1057

27 Oct 2006 21:24:47 IST

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Firstly, the answer u got is the correct one.It may be possible that it is given wrong in the book you refferred.

To find empirical formula follow the given steps:

1. for element A- 75/75.8 = .989

2. for element B: 16/24.2 = 0.66

3. get the simplest ratio as

for A - .989/.66 = 1.5 approx.

for B - .66/.66 = 1(divide both of them by the smaller one of the two)

4. so we get the formula

A₃B₂

hemang

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Joined: 27 Dec 2010

Posts: 1474

27 Jan 2011 11:43:23 IST

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A3B2

hemang

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Joined: 27 Dec 2010

Posts: 1474

27 Jan 2011 11:55:32 IST

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i am correct.

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