Chemistry help

[Nanobyte]

We took a quiz today on chemical equations and such in chemistry, and I'm wondering why I got a 70.. Here are the questions and my incorrect answers:

Write chemical equations for the following:

solid zinc sulfide + oxygen gas ---> solid zinc oxide + sulfurdioxide (an unbalanced compound, S has charge of 2 and O has charge of 4)
ZnS + 3O --> ZnO + SOsubscrict2

hydrochloric acid + agueous magnesium hydroxide ---> aqueous magnesium chloride + water
?

Carbon tetrachloride is produced by reacting chlorine gas with methane gas (CHsubscript4). Hyrdrogen chloride gas is also formed in the RXN(reaction).
8Cl + CHsubscript4 --> CClsubscript4 + 4HCl

Phosphoric acid is produced through the reaction of tetraphosphorus decaoxide (an unbalanced compound, P has charge of 12 and O has charge of 20) and water.
5Psubscript4Osubscript10 + 3OHsubscript2O --> 2OHsubscript3POsubscript4

Those 4 are the ones I missed that I do not understand. Any help is appreciated.

[Azred]

note: all numbers used below are subscripts.

Write chemical equations for the following:

solid zinc sulfide + oxygen gas ---> solid zinc oxide + sulfurdioxide
2ZnS + 3O2 --> 2ZnO + 2SO2

hydrochloric acid + agueous magnesium hydroxide ---> aqueous magnesium chloride + water
2HCl + Mg(OH)2 --> MgCl2 + 2H20

Carbon tetrachloride is produced by reacting chlorine gas with methane gas. Hyrdrogen chloride gas is also formed in the reaction.
4Cl2 + CH4 --> CCl4 + 4HCl

Phosphoric acid is produced through the reaction of tetraphosphorus decaoxide and water.
P4O10 + 6H2O --> 4H3PO4

Originally posted by Nanobyte: Those 4 are the ones I missed that I do not understand. Any help is appreciated.

It all comes down to simply counting ions on each side. Always start with the non-elemental ions first, then adjust the elements and the water to balance hydrogens and oxygens.
Oxygen gas is always represented in equations as O2; two atoms share two electron pairs. Chlorine gas is Cl2; two atoms share one electron pair.

[Davros]

Backing up Azred - on two of the questions (the first and third) you used Cl and O to represent Chlorine gas (Cl2) and Oxygen (O2). The last one you have a correct equation that is just a multiple of 5 bigger than the base equation (but a good bet the teacher wanted the base equation - they always do).

[WillowIX]

Originally posted by Davros: (but a good bet the teacher wanted the base equation - they always do

Lol they do, don´t they? But in real life I´d say you´re more correct nanobyte. Finding a reaction with only a single substrate is impossible (in real life again). Azred has give you your answers I see so I guess we have two future chemists on our board. Can I call you if I ever need some nitric acid or something?

[Davros]

I don't know about being a future Chemist - us Chemical Engineers heap light hearted derision on the straight Chemists for being too theoretical, and not practical enough.

[Nanobyte]

Originally posted by Azred: It all comes down to simply counting ions on each side. Always start with the non-elemental ions first, then adjust the elements and the water to balance hydrogens and oxygens. Oxygen gas is always represented in equations as O2; two atoms share two electron pairs. Chlorine gas is Cl2; two atoms share one electron pair.

Hmm.. I'm not fully understanding this. So you focus on balancing the hydrogrens and oxygens? On the element gases, I knew about hydrogen gas, H2, but then something got me confused on the matter of element gases. Do all element gases have two atoms?

[Andrew Mcveigh]

not all of them...

to know which elements have 2 atoms spell out the name HOFBrINCl

H= Hydrogen
O= Oxygen
F= Fluorine
Br=Bromine
I= Iodine
N= Nitrogen
Cl=Chlorine

if any of these elements are by themselves (not with another element, ie: H20, O isn't by itself), then there are 2 atoms. hope this helps!

PS: i just took a chemistry test today, i hope i did good!!!

[Nanobyte]

Originally posted by Andrew Mcveigh: not all of them... to know which elements have 2 atoms spell out the name HOFBrINCl H= Hydrogen O= Oxygen F= Fluorine Br=Bromine I= Iodine N= Nitrogen Cl=Chlorine if any of these elements are by themselves (not with another element, ie: H20, O isn't by itself), then there are 2 atoms. hope this helps! PS: i just took a chemistry test today, i hope i did good!!!

Oh! That is what they are for! Except I use BrINClHOF, it's German for something [img]tongue.gif[/img]

[Azred]

Originally posted by WillowIX: Azred has give you your answers I see so I guess we have two future chemists on our board. Can I call you if I ever need some nitric acid or something?

[img]graemlins/laugh3.gif[/img] Hardly future, Willow. I earned my degree 10 years ago. [img]graemlins/beigesmilewinkgrin.gif[/img]

[WillowIX]

Originally posted by Andrew Mcveigh: f any of these elements are by themselves (not with another element, ie: H20, O isn't by itself)

Wouldn´t it be easier to count the electrons in the atom? Since all but the inert gases needs more or less e^- to fill out their shells only the inert gases are capable of being single. That´s the most favorable state for them. For every other atom the omst favorable state is to be connected to another atom thereby gaining inert capability...