# Empirical Formula

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Hey guys,

Im stuck on some work ive got to do for later this week, heres the question:

chlorine gas is passed over phosphorus it is found that 6.28g of phosphorus yield 10.54g of a product. Work out the empirical formula of the product?.

So i think ive got to work out the ratios to get the formula.

Cl + P -> PCl

Then i tried to work out the number of moles of each but it didnt get me any clear ratios.

Can anyone help?

Thanks,

Jacky Logan

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You know how many grams of the final product is going to be from the phosphorus, right? So what's left must be just the chlorine, right? So there you go.

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You have to convert what you have in grams into moles. Then use the element with the least amount of moles and divided the number of moles of other element with this number. I have a feeling the phosphorus is going to have the least amount of moles.

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actually if the empirical formula is PCl, it could not be the trichloride or pentachloride. it could be $PCl$, $P_2Cl_2$, $P_3Cl_3$, etc.

however, none of those compounds are particularly stable, at all.

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i just tried working it out and found the ration of Cl : P as 1:1.688 which is weird since then, the empirical formula would round off to be P2Cl .... and I don't think thats right. Must be something wrong in the question or something or I, maybe, doing something wrong... [i just hate it when that happens!!]

-mak10

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I also get a ratio of Cl to P of 1.687, which is something like P5Cl3. As fas as I know, this is not a stable compound. However, the question was to calculate the "empirical formula", which means that it does not have to be a usefull stoichiometry for a single compound. You can argument that the product is a mixture of PCl3 and remaining unreacted phosphorus.

Regards,

m/z

Its PCl3

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