Balancing Chemical Equations - Is RHS=LHS true always?

  • #1
akerkarprashant
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TL;DR Summary
Balancing Chemical Reactions/Equations - Is RHS=LHS true always?
Below are some examples of Chemical Reactions/Equations.

2H2 + O2 = 2H2O
CU+ H2SO4=CUSO4 + H2
2MG + O2 =2MGO
2NA + CL2 =2NACL
and so on ....

I mean is RHS=LHS always true for all Chemical Equations or only for specific chemical equations or not true at all?

2H2O=2H2 + O2
CUSO4+H2=CU+H2SO4
2MG=MG + O2
2NACL=2NA + CL2
and so on ...

If True, False or Some True or False reasons for the same?
 

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Answers and Replies

  • #2
Borek
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Yes, by the very definition of "balanced".

Note that your notation is wrong, Na, not NA, Mg not MG and so on.
 
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  • #3
akerkarprashant
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Thanks.

My query was different.

From the given equations/reactions,

2H2O=2H2 + O2
CuSO4+H2=Cu+H2SO4
2MgO=2MG + O2
2NaCL=2Na + CL2

Can we derive/get Hydrogen gas and Oxygen gas from Water?
Can we derive/get Copper and Sulphuric Acid from Copper Sulphate and Hydrogen gas?
Can we derive/get Magnesium and Oxygen gas from Magnesium Oxide?
Can we derive Sodium and Chlorine gas from Sodium chloride?
The Above is possible using any Chemical processes?.
Is this possible in all Chemical Reactions or Few Chemical Reactions or not a single chemical reaction?
Will RHS=LHS work actually in Chemistry laboratories?
 
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  • #4
akerkarprashant
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If Yes, Can we say LHS=RHS and
RHS=LHS?

If Not, Why?

Thanks & Regards,
Prashant S Akerkar
 
  • #5
Borek
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Can we derive/get Hydrogen gas and Oxygen gas from Water?
Yes.

But: just because we can balance an equation doesn't mean it will proceed. Sometimes the whole process is doable, but will require many additional steps. As in practice each step means loses final amount of the product won't be ever equal to the theoretical one.

It is actually quite difficult to answer your question in a reasonable way, as it is based on some mix of idealized ideas and exact conservation laws.
 
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  • #6
sophiecentaur
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If Not, Why?
How could it not always be the case? Assuming that the reaction is actually possible, any imbalance would have to mean that some Atoms would be 'missing' or 'left over'. This is why we multiply both sides, appropriately so that the molecules on both sides of the equation are complete:
2H2O=2H2 + O2
At first sight, H2O = H2 + O
would balance but monatomic Oxygen is not around so the simplified equation doesn't describe real life. You have to 'double up' to describe what you get in a real experiment with real mass measurements and complete reactions with nothing left over.
Maths is the servant of Science and not the master.
 
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  • #9
pbuk
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Comment?
I think that the OP is actually asking about reversibility of reactions rather than whether they balance.
 
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  • #10
Ygggdrasil
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In chemistry, there is the principle of microscopic reversibility, which states that every elementary chemical reaction is reversible (an elementary chemical reaction is one that occurs in essentially one step and is not a chemical reaction representing a multistep process). For example, if two hydrogen molecules collide with an oxygen molecule to produce two water molecules, then it must be possible to two water molecules to collide and transform into 2H2 + O2 (in reality, the elementary steps of this transformation are different, for example, often the reaction occurs on a solid surface, such as a catalyst in an electrolyzer or fuel cell, where the hydrogen and oxygen molecules form partial bonds with the surface, weakening the hydrogen-hydrogen and oxygen-oxygen bonds). A better example of an elementary chemical reaction that exhibits microscopic reversibility might be an water molecule going from the vapor phase to the liquid phase (or vice versa), a sodium or chloride ion binding/unbinding to a sodium chloride crystal in a salt solution, or a water molecule hydrolyzing the peptide bond of a protein.

Note that just because a reaction is reversible does not always mean it will be easy to get it to proceed either way. One must consider the thermodynamics of the reaction to see which direction is thermodynamically unfavorable and whether the conditions of the reaction (e.g. changing the temperature or pressure can favor liquid water vs water vapor) must be changed to get the reaction to favor one side or the other or if an outside source of energy must be added (e.g. hydrogen and oxygen combine explosively to form water but to get these gasses from water molecules, you must add in energy, for example, via electrolysis).
 
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  • #11
sophiecentaur
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One must consider the thermodynamics of the reaction to see which direction is thermodynamically unfavorable and whether the conditions of the reaction (e.g. changing the temperature or pressure can favor liquid water vs water vapor) must be changed to get the reaction to favor one side or the other or if an outside source of energy must be added (e.g. hydrogen and oxygen combine explosively to form water but to get these gasses from water molecules, you must add in energy, for example, via electrolysis).
This is the essence of the subject. The Chemical Energy on one side of the equation (mutual 'attractions' of the atoms) will be different from the Energy on the other and Energy needs to be supplied to the system to reverse it - this can be in be with electrolysis or (as in reduction processes) by introducing another element or compound which presents an even lower Energy situation by displacement of atoms.
Alternatively, if the energy difference is small enough, then both states are possible to exist at the same time and the 'two way arrows' in the equation can be added.
 
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