[getfirefox]

Hi guys. I was just wondering if someone could help me out by maybe going through this example with me. My problem is to do with Chemical Formulae.

I am comfortable with the idea of n = mass (g) / Ar and have been using it to work out formula for questions such as "Calculate the formulae of the compounds which contain only the elements shown. 2.0g of hydrogen and 16.0g of oxygen" without any problem.

But, I am stuck on this one. Anyone know how I'd go about solving it?

"What is the empirical formulae of C₃H₆."

I know the answer is CH₂, (I looked up the answer) but I have no idea how to get it.

Can anyone explain? Thanks!

[Astrokel]

hey getfirefox,

empirical formula is the simplest relative ratio of elements in a compound.

"What is the empirical formulae of C3H6."

You have to assume C3H6 is molecular formula which represents the actual ratio of elements in a compound. So, its empirical formula is the simplest ratio which is CH2.

It's the same as C6H6(molecular formula), therefore the empirical is CH. Note the ratio is an integer.

[getfirefox]

Can you explain how you worked this out? How exactly did you end up with that answer? Sort of step-by-step.

Thanks for helping.

[Astrokel]

hey,

you have to understand the definition of empirical and molecular formula first as i have previously defined.

http://en.wikipedia.org/wiki/Empirical_formula

Since they want the empirical formula of C₃H₆ which is the SIMPLEST RATIO of the ELEMENTS in the COMPOUND,

you get CH₂ since (CH₂) x 3 = C₃H₆

It's like, you have 3 blue beans and 9 red beans, whats the ratio of blue to red, 1:3, ye? so 3:9 is like the molecular formula and 1:3 like empirical

[getfirefox]

hey,

you have to understand the definition of empirical and molecular formula first as i have previously defined.

http://en.wikipedia.org/wiki/Empirical_formula

Since they want the empirical formula of C₃H₆ which is the SIMPLEST RATIO of the ELEMENTS in the COMPOUND,

you get CH₂ since (CH₂) x 3 = C₃H₆

It's like, you have 3 blue beans and 9 red beans, whats the ratio of blue to red, 1:3, ye? so 3:9 is like the molecular formula and 1:3 like empirical

Ah. Thanks mate.

I think I see now.

So its just the smallest number I can get by dividing without getting a fraction?

For example,

P₄O₆ ---> P₂O₃

Is that correct?

[Borek]

Yes. From mass analysis you can find just a molar ratio, so that's all you know before you check molar mass,