How do you write balanced half equations?

To write balanced half equations, you need to balance the atoms and charges on both sides of the equation.

Balancing half equations is a crucial part of understanding redox reactions in chemistry. A half equation is written for the oxidation or reduction process, showing what happens to the reactant as it loses or gains electrons. Here's a step-by-step guide on how to balance half equations:

1. Write down the unbalanced equation: Start by writing down the unbalanced equation, which includes the reactant and the product.

2. Balance the atoms: Balance all atoms other than O and H. If the same atom appears on both sides of the equation, make sure there is an equal number of them.

3. Balance the oxygen atoms: If there are oxygen atoms, balance them by adding H2O to the side that needs more oxygen.

4. Balance the hydrogen atoms: If there are hydrogen atoms, balance them by adding H+ ions to the side that needs more hydrogen.

5. Balance the charge: Finally, balance the charges on both sides of the equation by adding electrons (e-) to the side that has a more positive charge.

For example, let's balance the half equation for the reaction where chlorine is reduced to chloride ions: Cl2 -> 2Cl-.

1. Write down the unbalanced equation: Cl2 -> 2Cl-.
2. Balance the atoms: The chlorine atoms are already balanced.
3. Balance the oxygen atoms: There are no oxygen atoms in this equation.
4. Balance the hydrogen atoms: There are no hydrogen atoms in this equation.
5. Balance the charge: The left side of the equation has no charge, while the right side has a charge of -2. To balance the charges, we add 2 electrons to the left side of the equation: Cl2 + 2e- -> 2Cl-.

Remember, practice makes perfect. The more you practice balancing half equations, the more comfortable you'll become with the process.