Blakhitman's chem questions thread!

[Blakhitman]

Thanks guys, I remember my methods teacher telling me how to remember now, something bout S.P.A.N.N.E.R, or was it S.P.A.N.N.A anyway I tried googling it but couldn't find anything on it and I can't remember what it means, anyone know this method?

Got it off teacher Spana Chops....Doesn't contain everything though.

SPANA

Compounds containing Sodium Potassium Ammonium Nitrate and Acetate ions are always soluble in water.

CHOPS

Compounds containing Carbonate Hydroxide Oxide Phosphate and Sulfide ions are generally water insoluble unless combined with SPANA ions.

Still, I think it can be quite useful.

[Blakhitman]

To separate these into half equations...would I write a half equation for both HgO into Hg, and HgO into O2?

[Mao]

To separate these into half equations...would I write a half equation for both HgO into Hg, and HgO into O2?

Yes

[Blakhitman]

To separate these into half equations...would I write a half equation for both HgO into Hg, and HgO into O2?

Yes

Thanks a lot!

Why the hell didn't I discover this place in year 11?!

[Mao]

To separate these into half equations...would I write a half equation for both HgO into Hg, and HgO into O2?

Yes

Thanks a lot!

Why the hell didn't I discover this place in year 11?!

No worries. Here's some more for exercise.

Separate into two redox half equations:
a)
b)

[Blakhitman]

Thanks Mao, you're a legend!

Ok need help with this... how would I go about working it? Thanks in advance to anyone that can help!

An organic compound underwent combustion. it was known to contain only Carbon, Hydrogen and Oxygen. It was analysed by burning a 1.00g sample in air. If 1.91g of CO2 and 1.17g of H2O was produced, what was the empirical formula of the compound.

[fady_22]

First calculate the number of moles of carbon dioxide and water:




From this, you can calculate the number of mole of hydrogen and carbon in the compound:
and

Now you can calculate the masses of both carbon and hydrogen in the sample, and subtract the masses from the mass of the organic compound, giving 1-0.65=0.35 g of Oxygen.

Now, find the number of mole of oxygen:


Now that you have the number of mole of carbon, hydrogen and oxygen, you can find the ratio in which they are found in the compound:
n(C):n(H):n(O)
2:6:1
Therefore, the empirical formula is:

[Blakhitman]

Thank you so much!

And is your name really Fady?

[fady_22]

Thank you so much!

And is your name really Fady?

Just saw your email... your name is Fady too lol.

[Blakhitman]

Ok, was just wondering as my name is also Fady ><

Pretty cool almost same subjects too.

[Blakhitman]

Thank you so much!

And is your name really Fady?

Just saw your email... your name is Fady too lol.

haha yep

[Blakhitman]

First calculate the number of moles of carbon dioxide and water:




From this, you can calculate the number of mole of hydrogen and carbon in the compound:
and

Now you can calculate the masses of both carbon and hydrogen in the sample, and subtract the masses from the mass of the organic compound, giving 1-0.65=0.35 g of Oxygen.

Now, find the number of mole of oxygen:


Now that you have the number of mole of carbon, hydrogen and oxygen, you can find the ratio in which they are found in the compound:
n(C):n(H):n(O)
2:6:1
Therefore, the empirical formula is:

O.k I forgot to give you some info, would it matter if I gave you the equation of the process? or would it just make it easier?

Yes that includes the molecular formula  

C2H2O + 2O2 --> 2CO2 + H2O

EDIT: wait can't I just use the 1.00 g to work out the mol of Carbon, Hydrogen and Oxygen in the compound given the formula of it? then do ratios? Man chem is confusing.

[Blakhitman]

Why is each of the elements, Nitrogen, Phosphorus, Sulfur and Iron included in Lawn food?

[Edmund]

http://lmgtfy.com/?q=Why+is+each+of+the+elements%2C+Nitrogen%2C+Phosphorus%2C+Sulfur+and+Iron+included+in+Lawn+food%3F

Apparently someone asked the same question on Yahoo Answers

[the.watchman]

http://lmgtfy.com/?q=Why+is+each+of+the+elements%2C+Nitrogen%2C+Phosphorus%2C+Sulfur+and+Iron+included+in+Lawn+food%3F

Apparently someone asked the same question on Yahoo Answers

LOL, i'm so over lmgtfy...