The first preparation of chlorine was similar to the synthesis of elemental bromine (Problem 22.146). A later method entailed the reaction of hydrogen chloride and oxygen at 400 °C. Write a balanced equation for the reaction. (Water is also formed.)

Verified step by step guidance

1. Step 1: Identify the reactants and products in the reaction. The reactants are hydrogen chloride (HCl) and oxygen (O2), and the products are chlorine (Cl2) and water (H2O).
2. Step 2: Write the unbalanced chemical equation using the chemical formulas of the reactants and products: HCl + O2 → Cl2 + H2O.
3. Step 3: Balance the chlorine atoms. There are two chlorine atoms in Cl2, so you need two HCl molecules to provide two chlorine atoms: 2 HCl + O2 → Cl2 + H2O.
4. Step 4: Balance the hydrogen atoms. There are two hydrogen atoms in 2 HCl, so you need one H2O molecule to balance the hydrogen: 2 HCl + O2 → Cl2 + H2O.
5. Step 5: Balance the oxygen atoms. There are two oxygen atoms in O2 and one oxygen atom in H2O, so you need to adjust the coefficients to balance the oxygen atoms: 4 HCl + O2 → 2 Cl2 + 2 H2O.