In a chemical eauqtion, do all elements in thereactants side haveto be present in the product side?

Question

how woould i balance such equation?

Answer 1

yes every atom you have on the reactant side must show up on the product side.

The reason for this is because of the law of conversation of matter and energy, which says you can't create or destroy matter. Since no atoms randomly disappear or appear out of air, then it's important to show in your equations that you didn't lose or add any atoms. The way you do that is by balancing equations.

To balance equations, you multiply the coefficients of the compounds (not the subscripts, otherwise that would change the compound entirely!) and keep working with them until you have the same "number" of atoms on both sides.

For example, say you have something like:
C2H6 + O2 ---> CO2 + H2O

We see that you start with 2 carbons, but end up with 1?? Or we start with 6 hydrogens, but end with 2?? Obviously this doesn't make sense, so we balance the equation to this effect:

2(C2H6) + 7(O2) ---> 4(CO2) + 6(H2O)

And you can see that on both sides you have:
4 carbon atoms
12 hydrogen atoms
14 oxygen atoms
Which is balanced!

Answer 2

Yes, this is the 'Conservation of Matter'.
In the reaction, nothing is actually lost even though a gas for example dissipates into the atmosphere.
When Propane gas is burned, the reactants are converted into the products with no loss of any elements.
The unbalanced equation will be:
C3H8(g) + O2(g) = CO2(g) + H2O(vapour (or gas)).
(3 x C) + (8 x H) + (2 x O) = (1 x C) + (2 x H) + (3 x O).
It can be seen that the number of 'C's , 'O's and 'H's on the left of the '=' sign are less than on the right.
To balance the equation we need to adjust the number of elements. We will get...
C3H8 + 5O2 = 3CO2 + 4H2O.
= (3 x C) + (8 x H) + (10 x O)
= (3 x C) + (8 x H) + ((6 x O) + (4 x O))

Answer 3

Yes.. because matter can not be destroyed or created..

you can't change the subscripts in an equation, but you can change the coefficients to make the number of atoms on each side (of each element) equal