[Winter]

Hello!

I've been tackling this subject quite a while now.

Essentially the problems are these:

I.Balance and write out the rule

Fe + CuS =
Rule:

Al + MgSO₃ =
Rule:

K + O₂ =
Rule:

Na + O₂ =
Rule:

Li + H₂O =
Rule:

Now I have printed out a large amount of chemical reaction related material but I still can't seem to understand this.

Using a reaction solver: Fe + CuS = Cu + FeS

So Fe is a Metal Cu is also a metal where as S is not a metal,
my rule states that metal + nonmetal depends on the metals activity?
like Fe + S -> FeS

How can I determine that Fe + CuS equals Cu + FeS?
I can't see any logic behind this.

[Arkcon]

Ok, I'm not surprised that you're having trouble finding the logic behind chemical reactions.  We write them like math problems, but they follow different rules, that you have to learn.  You'd close 'tho, so we can work to fill in what you need.

Your first one is a good one, you recognize the difference between metal and non-metal and how they work.  But now you need to research reactivity.  There are tables in your textbook or online, but lets try to use some logic that you crave, based on what you've seen around the world we all live in.

Which is more reactive -- iron or copper?  Which have you more often seen, shiny and bright, without paint -- copper or iron?  Have you even seen a lump of sodium metal, on the ground, and picked it up and put it in your pocket?  (IF you know why you'd never do that, then you have a logical answer for that question.)  Have you ever seen corroded gold or platinum?  That aluminum vs magnesium is going to be tricky, without a table, however.

[Winter]

Still being on the Fe + CuS

Fe is iron so a metal and so is Cu Copper but S is a nonmetallic element.

Looking at the reactivity scale  Iron is more active than Copper.

The answer that i Found was Cu + FeS

So going by crude logic   
More active Metal + Less Active metal&Nonmetal = less active metal + More active metal&non metal?

Why does the non metal element attach to Iron?
Essentially what i see is that the metals switch according to their place in the activity scale?

So - Al + MgSO₃ would equal Mg + AlSO₃ ?
Does the index play any role?

[Winter]

So I have conducted more research on this.

Fe + CuS =

Fe is Iron so it is a metallic element
CuS though there is Copper in there, but due to S it turns into Salt  /?/

The rule states that the salt has to be dissolvable and the metal has to be more active than the metal in the salt. Fe is indeed higher on the activity scale than copper

Therefor the equation equals Cu + FeS.
I learned about ionic charges  so the end answer should be
Cu + Fe₂S₂.
The rule is metal + salt.

Moving onto Al + MgSO₃

Al is a metal.
Mg is also a metal.
MgSO is essentially a salt cause of rules.
So again looking at the activity Mg is higher than Al.
The rule states that the metal has to be more active than the metal in the Salt.
In which case i feel like shooting myself because this seems to not make sense.
Breaking the rule I still solve the equation like this
Mg + Al(SO₃)₃
The rule is metal + salt

Next we have K + O₂
K is a metal .
O₂ is something else.
The rules states essentially nothing.
The answer turns out to be K₂O because O has an Ionic charges of 2 and we leave the 2 from before behind so we are left with that.
The rule is metal + nonmetal

Na + O₂
Na is a salt.
O₂ i dont know.
Going by what what I've learned
the answer is Na₂O
The rule is salt + base

Lastly we have Li + H₂O
Li is a metal
H20 is water
I've come to an answer that this equals LiO + H₂

So after hours of research I have come to a conclusion.
....What?

[Winter]

Actually!!

Fe + Cus = Cu + FeS
Is WRONG
Since there exists somekind of a solvent table where it says

Fe is solvable with S so the answer is Not solvable

same goes for Al + MgSO3

K+O2 was right so was Na+O2 and the last one

[Borek]

Actually!!

Fe + Cus = Cu + FeS
Is WRONG
Since there exists somekind of a solvent table where it says

Fe is solvable with S so the answer is Not solvable

To make things more confusing and difficult, the reaction doesn't have to take place in solution (solids react much slower, or they require elevated temperatures to react in a reasonable time, but they do react, google for thermite reaction). Just by looking at the reactivity series one could expect it to proceed (Fe being more reactive than Cu), but actually you should take into account several other factors. Without calculating ΔG for the reaction I have no idea what the real outcome is.

Next we have K + O₂
K is a metal .
O₂ is something else.
The rules states essentially nothing.

Almost every metal (except noble ones) reacts easily with oxygen, creating oxides.

Na is a salt.

No.

Lastly we have Li + H₂O
Li is a metal
H20 is water
I've come to an answer that this equals LiO + H₂

Close, but LiO is not the product here. First, because it doesn't exist (think what is valence of Li and what is valence of oxygen), second, because even if the lithium oxide were the product, it would react easily with water.

[Winter]

Fairly clueless at this point.
Well even more clueless actually.

I don't need to take in account the other factors in the solution.
Since I just have a test on the simple part and don't really need the other factors.

So on the test Fe + CuS = doesn't react
would account as right.

So essentially I want to understand when where and how do I know that
this thing switches and that thing switches like that.

[Arkcon]

Fairly clueless at this point.  Well even more clueless actually. 

Yes.  As Borek: highlighted, you're making up random rules, that don't describe our universe at all.  Try an actual chemistry textbook, instead.

I don't need to take in account the other factors in the solution.  Since I just have a test on the simple part and don't really need the other factors.

Yes you do, if you are to predict a reaction.  Which is what you said you had to do.  Or not, if you're going to make  a collection of simple rules, for more teaching later on.

So on the test Fe + CuS = doesn't react would account as right.

Sure.  In water.  If the instructor meant melted together, than no, you would end up with a puddle of copper, some iron sulfide, and some released sulfur.  Stay with the first one result, but don't be too shocked if the second one was what the instructor was looking for.  Small hint:  in water, none of your reactions will work at all, so this will be a short problem set, if you include water, which you didn't mention  at the start.

So essentially I want to understand when where and how do I know that this thing switches and that thing switches like that.

We've given you a start, but you switched to water solution.  Why not try some examples that are actually in water solution.