[Lindsay]

Hello,
Here is the problem,
When 0.667-g sample of the mercury oxide is heated , 0.618 g of mercury metal remains.
a. What is the mole ratio of mercury to oxygen in the sample?
b What is the empirical formula of the mercury oxide?

For a, I did the following?

0.618 g Hg X 1mol/200.6 = .00308 mol Hg / .00306 = 1
0.049 g O  X 1mol/16.00 = .00306 mol O  /  .00306 = 1
the mole ratio of Hg atoms to oxygen atoms is 1:1

b The empirical formula for the compound is FeO

Please let me know if it is correct.
Also, is not the oxygen supposed to be a diatomic molecule? I was not sure whether or not I needed to use it in the above problem.

Please advice,

Lindsay

[nj_bartel]

You wrote the empirical formula as FeO, but I believe that was just a typo as you wrote mercury as Hg earlier (which is correct).

Yes, oxygen is a diatomic molecule, but you don't need to treat it as such in this problem.

Your answers look good to me.

[Lindsay]

Thanks so much for your quick response.
Yes, it should be HgO or Mercuric Oxide

As for the diatomic molecules, How do you know when to treat them as diatomic or not? Is there a way to that?
If I see O, H, Cl, I would think they are diatomic and I would perhaps treat them as two molecules
Just like if I get this problem
sodium reacts with chlorine to form Sodium chloride, right? When you write the equation like
Na + Cl ----- NaCl
That's wrong, right?
it should be
2Na + Cl2---2NaCl

I'm just somewhat confused about when to treat them as diatomic and when not

Please advise

Lindsay

[Borek]

How do you know when to treat them as diatomic or not? Is there a way to that?

Simple rule to remember: H₂, N₂, O₂ and all halogens are always diatomic.