How do you balance the chemical equations for double replacement reactions?

Question

Owen Ambrose · Accepted Answer

You balance double replacement equations by pairing each cation with the anion from the other compound in the correct ratios.

Example

Write a balanced equation for the reaction between Fe(NO₃)₂ and Na₃PO₄.

Solution

Identify the cations and anions in each compound:
Fe(NO₃)₂ has Fe²⁺ and NO₃⁻
Na₃PO₄ has Na⁺ and PO₄³⁻

Pair up each cation with the anion from the OTHER compound:
Fe²⁺ pairs with PO₄³⁻
Na⁺ pairs with NO₃⁻

Write two new (CORRECT!!) formulas using the pairs from
Step 2.
Fe₃(PO₄)₂, since Fe is +2 and PO₄ is -3
NaNO₃ since Na is +1 and NO₃ is -1

Write the unbalanced equation
Fe(NO₃)₂ + Na₃PO₄ → Fe₃(PO₄)₂ + NaNO₃

Balance the equation.
The Fe₃(PO₄)₂ has 3 Fe and 2 PO₄ on the right, so you need 3 Fe and 2 PO₄ on the left:
3Fe(NO₃)₂ + 2Na₃PO₄ → Fe₃(PO₄)₂ + NaNO₃

Now we have 6 NO₃ on the left, so we need 6 NO₃ on the right.

The balanced equation is
3Fe(NO₃)₂ + 2Na₃PO₄ → Fe₃(PO₄)₂ +6NaNO₃

Here is a video to help with balancing double replacement reactions.

Caleb Adams · Answer

undefined The procedures listed below can be used to balance the chemical equations for double replacement reactions: 1. Write down the equation that is out of balance; 2. Identify the reactants and products, making sure they are accurately represented; 3. Ascertain the charges of the ions in the reactants and products; 4. Exchange cations and anions between the reactants to form new products; 5. Write the chemical formulas of the new products; 6. Balance the equation by adjusting the compounds' coefficients as necessary to guarantee that there are equal numbers of atoms of each element on both sides of the equation; 7. Confirm that the charges are also balanced.

Serenity Allen · Answer

undefined To balance chemical equations for double replacement reactions, follow these steps:

1. Write down the unbalanced equation.
2. Identify the reactants and products.
3. Write the chemical formulas for each compound correctly.
4. Determine the ions present in each compound.
5. Use the charges of the ions to ensure that the total charge is the same on both sides of the equation.
6. Balance the equation by adjusting coefficients to make the number of atoms of each element the same on both sides.
7. Verify that the equation is balanced by counting the number of atoms of each element on both sides of the equation.

Repeat these steps as needed until the equation is balanced.