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)
<font color=red>ZnS + 3O --> ZnO + SOsubscrict2</font>

hydrochloric acid + agueous magnesium hydroxide ---> aqueous magnesium chloride + water
<font color=red>?</font>

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

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.
<font color=red>5Psubscript4Osubscript10 + 3OHsubscript2O --> 2OHsubscript3POsubscript4</font>

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

<font color = lightgreen>note: all numbers used below are subscripts.</font>

Write chemical equations for the following:

solid zinc sulfide + oxygen gas ---> solid zinc oxide + sulfurdioxide
<font color = lightgreen>2ZnS + 3O2 --> 2ZnO + 2SO2</font>

hydrochloric acid + agueous magnesium hydroxide ---> aqueous magnesium chloride + water
<font color=lightgreen>2HCl + Mg(OH)2 --> MgCl2 + 2H20</font>

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

Phosphoric acid is produced through the reaction of tetraphosphorus decaoxide and water.
<font color=lightgreen>P4O10 + 6H2O --> 4H3PO4</font>

<font color = lightgreen>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.</font>

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).

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? :D :D

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. :D

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?

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]

<font color = lightgreen> [img]graemlins/laugh3.gif[/img] Hardly future, Willow. I earned my degree 10 years ago. [img]graemlins/beigesmilewinkgrin.gif[/img] </font>

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...