To balance the given chemical equation:
Unbalanced equation:
\[ 2 \text{NaHCO}_3 \rightarrow \text{Na}_2\text{CO}_3 + \text{CO}_2 \]
Let’s break down the reactants and products:
-
Reactants:
- 2 Na (from 2 NaHCO3)
- 2 H (from 2 NaHCO3)
- 2 C (1 from Na2CO3 and 1 from CO2, total of 2)
- 6 O (from 2 NaHCO3 contributing 3 per molecule, total of 6)
-
Products:
- 2 Na (from Na2CO3)
- 2 C (1 from Na2CO3 and 1 from CO2)
- 5 O (3 from Na2CO3 and 2 from CO2)
Currently, the equation is not balanced because the number of oxygen atoms on the products side is 5, while there are 6 on the reactant side (according to the breakdown above).
To balance the number of oxygen atoms, we can look for a compound that can provide one additional oxygen atom without disturbing the balance of other elements.
Of the options given:
- H2: does not provide oxygen
- CH2OH: does not provide oxygen (it contains 1 O)
- H2O: provides 1 O, making the total oxygen count 6
- O2: provides 2 O, which would unbalance the equation further
The correct addition to balance the equation is:
H2O