How to Balance the Decomposition Reaction of Magnesium Nitrate

To "balance magnesium nitrate" in the context of a chemical reaction refers to balancing a chemical equation where magnesium nitrate is involved. The most common reaction involving balancing magnesium nitrate is its thermal decomposition.

Balancing a chemical equation ensures that the Law of Conservation of Mass is upheld, meaning the number of atoms for each element is the same on both the reactant and product sides of the equation.

The decomposition of magnesium nitrate (Mg(NO3)2) typically yields magnesium oxide (MgO), nitrogen dioxide (NO2), and oxygen gas (O2).

Unbalanced Equation:

Mg(NO3)2 (s) → MgO (s) + NO2 (g) + O2 (g)

Here’s a step-by-step guide to balancing this reaction:

Step 1: Count Atoms on Both Sides

List the number of atoms for each element on the reactant and product sides of the unbalanced equation.

At this stage, Magnesium (Mg) is balanced, but Nitrogen (N) and Oxygen (O) are not.

Step 2: Balance Elements Other Than Oxygen and Hydrogen (Typically N first)

Nitrogen (N) is present in 2 atoms on the reactant side (from Mg(NO3)2) and 1 atom on the product side (from NO2). To balance nitrogen, place a coefficient of 2 in front of NO2.

Equation Update:

Mg(NO3)2 → MgO + 2NO2 + O2

Step 3: Re-count Atoms and Balance Oxygen

Now, let's update the atom count, focusing on Oxygen.

Oxygen is now 6 on the reactant side and 7 on the product side. To balance oxygen, we need to adjust the coefficients further.

• Reference Insight: At this stage, or in a similar context, a common strategy involves aiming to match the oxygen count. As highlighted in the reference, one might count the oxygen atoms from the reactant side (e.g., 6 oxygens from one Mg(NO3)2 molecule) and then attempt to balance the product side to match a multiple of this value. The video segment "That means i now have 2 times the 1 i have 2 oxygens. Here plus the two here plus these two and that gives me six oxygen" suggests a calculation where product oxygen contributions sum up to 6 at a certain point. To achieve 6 oxygens on the product side while maintaining balanced Mg and N:
  • We have 1 O from MgO and 4 O from 2NO2, totaling 5 O.
  • We need 1 more O from O2. This means we need 1/2 of an O2 molecule.
  • Mg(NO3)2 → MgO + 2NO2 + 1/2 O2

Step 4: Eliminate Fractions (If Any)

To ensure whole number coefficients, multiply the entire equation by the smallest integer that clears all fractions. In this case, multiply by 2 to eliminate the 1/2 coefficient for O2.

Final Balanced Equation:

2Mg(NO3)2 (s) → 2MgO (s) + 4NO2 (g) + O2 (g)

Step 5: Final Verification

Let's recount all atoms in the final balanced equation to confirm:

All elements are balanced on both sides of the equation.