Which additional product balances the following chemical reaction? 2 C2H2 (g) + 5 O2 (g) → 4 CO2 (g) + _______

• A. 2 CO (g)
• B. 2 H2O (g)
• C. 2 O2 (g)
• D. 4 H2O (g)

Answer: (B)

Verified step by step guidance

1. Identify the reactants and products given in the chemical equation: 2 C2H2 (g) + 5 O2 (g) → 4 CO2 (g) + _______. Notice that 2 CO (g) is also mentioned as a possible product.
2. Write down the number of atoms of each element on the reactant side: For 2 C2H2, there are 4 carbon (C) atoms and 4 hydrogen (H) atoms; for 5 O2, there are 10 oxygen (O) atoms.
3. Count the atoms on the product side with the given 4 CO2 molecules: 4 CO2 contains 4 carbon atoms and 8 oxygen atoms. Since carbon atoms are balanced (4 on each side), focus on balancing hydrogen and oxygen atoms next.
4. Since there are 4 hydrogen atoms on the reactant side, the product side must contain hydrogen atoms as well. Water (H2O) is a common product in combustion reactions involving hydrocarbons, so add water molecules to balance hydrogen atoms.
5. Balance oxygen atoms by ensuring the total oxygen atoms on the product side (from CO2 and H2O) equal the oxygen atoms on the reactant side. Use the equation: Total O on reactants = O in CO2 + O in H2O, and solve for the number of H2O molecules needed.