Gaseous CO2 decomposes to form the gases CO and O2.

Will it be CO2--> CO+O2
or CO+O2-->CO2?

I know the solution above isn't balanced yet. I just have add the 2 behind CO2 and CO to make it balanced.

It is the first one.

Need 25.25 g of each reactant for CO2 +O2 + CO2

To determine the correct balanced equation for the decomposition of gaseous CO2 to form the gases CO and O2, we need to apply the principles of chemical reactions and balancing equations.

The given equation, CO2 → CO + O2, is not yet balanced, as you correctly pointed out. We need to balance it by ensuring that the same number of atoms are present on both sides of the equation. First, let's count the number of atoms for each element involved:

On the left side (reactants):
- Carbon (C): 1
- Oxygen (O): 2

On the right side (products):
- Carbon (C): 1
- Oxygen (O): 3 (1 in CO + 2 in O2)

Since oxygen is unbalanced, we need to equalize the number of oxygen atoms on both sides by adjusting the coefficient in front of CO2 and CO.

The balanced equation is:

CO2 → 2CO + O2

Here's how you can derive this balanced equation step by step:

1. Start with the unbalanced equation: CO2 → CO + O2.
2. Count the number of atoms for each element: C, O.
3. Observe the number of atoms on the reactant and product sides.
4. To balance carbon, the coefficient in front of CO is already balanced.
5. To balance oxygen, we have 2 oxygen atoms on the reactant side and 3 on the product side.
6. Add a coefficient of 2 in front of CO2 (which now gives us 2 carbon atoms and 4 oxygen atoms on the left side).
The equation becomes: 2CO2 → CO + O2.
7. Now, we have 4 oxygen atoms on the reactant side and 4 oxygen atoms on the product side. Oxygen is now balanced.
8. Finally, we need to balance carbon. By adding a coefficient of 2 in front of CO, we achieve balance for carbon as well.
The final balanced equation is: 2CO2 → 2CO + O2.

Remember, balancing equations is an essential skill in chemistry, ensuring that the law of conservation of mass is upheld.