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Topic: Equivalent Weights  (Read 4961 times)

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Offline jaychouf4n

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Equivalent Weights
« on: April 03, 2008, 02:56:38 AM »
Question:

Reaction of a main group chloride (24.71g) with ammonia (10.9g) gave a mixture of products consisting of NH4Cl (25.68g), a solid element A (2.57g) and  a yellow crystalline nitride of this element (7.37g) according to the equation below

nAwClx + mNH3 ---> pNH4Cl + qA + rAyNz

(where n, m, p, q, r, w, x, y, and z are coefficients to be determined).

I've tried solving this with simultaneous equations but i get 9 variables and 6 equations, so that can't work.

It should be done with equivalent weights but at the moment I am not really sure how. I think it has something to do with the chloride, since it has a valency of 1.

Offline Borek

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Re: Equivalent Weights
« Reply #1 on: April 03, 2008, 04:20:44 AM »
Cl in chlorides is 1 and N in nitrides is 3.

Concentrate on finding what A is. You can relatively easy calculate total mass of A, this will give you information of molar ratio of A/Cl and A/N in both compounds. Then it is trial and error - see what are A molar masses for different possible compositions of both compounds and look for the one that fit both.

Hint: A valence changes between chloride and nitride.

Once you know what are formulas of both compounds balancing is not that hard.
« Last Edit: April 03, 2008, 04:47:24 AM by Borek »
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Offline jaychouf4n

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Re: Equivalent Weights
« Reply #2 on: April 03, 2008, 04:43:01 AM »
There are p Cl in the product.

So the weight of NH4Cl is 53.492g

So the coefficient of p is 0.5 since there's 25.68g of NH4Cl

That means nx=0.5


Offline DrCMS

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Re: Equivalent Weights
« Reply #3 on: April 03, 2008, 04:48:39 AM »
There are p Cl in the product.

So the weight of NH4Cl is 53.492g

So the coefficient of p is 0.5 since there's 25.68g of NH4Cl

That means nx=0.5



Try your maths again 25.68/53.492 = ?

Offline Borek

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Re: Equivalent Weights
« Reply #4 on: April 03, 2008, 04:49:33 AM »
Sorry, I have edited my post in the meantime, reread it once again.

That means nx=0.5

No. Both n and x are integers.
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Offline jaychouf4n

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Re: Equivalent Weights
« Reply #5 on: April 03, 2008, 05:11:17 AM »
So taking this on...

The valency of Cl is 1 so the w is equal to 1.

so its nAClx

with the nitride it becomes rA3Nz

uh so the valency of A is not equal to 3, and therefore has to be 1,2 or 4.




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