Which of the following is unbalanced A. SnO2 + H2 → Sn + 2 H2O
B. 2Na + 2H2O → 2NaOH + H2
C. N2O5 + H2O → HNO3
D. 2Fe + 3Cl2 → 2FeCl3

The unbalanced chemical equation is;

C. N₂O₅ + H₂O → HNO₃

Explanation:

In balancing a chemical reaction equation, only the coefficients of the terms of the reactants and/or the products are adjusted (and not the subscripts to the atoms in the compounds) to ensure that the total number of each element is the same on either side of the arrow for the chemical reaction

A coefficient term is the number multiplier of the compounds and elements in a chemical reaction

Therefore, the balanced chemical equation is obtained by changing the coefficient of the product from the implied '1' to a '2' as follows;

N₂O₅ + H₂O → 2HNO₃