How to balance a skeletal equation?
How to balance a skeletal equation?
Below are guidelines for writing and balancing chemical equation.
- Determine the correct chemical formulas for each reactant and product.
- Write the skeleton equation.
- Count the number of atoms of each element that appears as a reactant and as a product. If a polyatomic ion is unchanged on both sides of the equation, count it as a unit.
- Balance each element on at a time by placing coefficients in front of the formulas. No coefficient is written for a 1. It is best to begin by balancing elements that only appear in one formula on each side of the equation. NEVER change the subscripts in a chemical formula – you can only balance equations by using coefficients.
- Check each atom or polyatomic ion to be sure that they are equal on both sides of the equation.
- Make sure that all coefficients are in the lowest possible ratio. If necessary, reduce to the lowest ratio.
Sample Problem: Balancing Chemical Equations Aqueous solutions of lead(II) nitrate and sodium chloride are mixed. The products of the reaction are an aqueous solution of sodium nitrate and a solid precipitate of lead(II) chloride.
Step 1: Plan the problem.
Follow the steps for writing and balancing a chemical equation.
Step 2: Solve.
Write the skeleton equation with the correct formulas.
Pb(NO3)2(aq)+NaCl(aq)→NaNO3(aq)+PbCl2(s)
Count the number of each atom or polyatomic ion on both sides of the equation.
reactants products 1 Pb atom 1 Pb atom 2 NO3- ions 1 NO3- ions 1 Na atom 1 Na atom 1 Cl atom 2 Cl atoms
The nitrate ions and the chlorine atoms are unbalanced. Start by placing a 2 in front of the NaCl. This increases the reactant counts to 2 Na atoms and 2 Cl atoms. Then place a 2 in front of the NaNO3. The result is:
Pb(NO3)2(aq)+2NaCl(aq)→2NaNO3(aq)+PbCl2(s)
The new count for each atom and polyatomic ion becomes:
reactants products 1 Pb atom 1 Pb atom 2 NO3- ions 2 NO3- ions 2 Na atom 2 Na atom 2 Cl atoms 2 Cl atoms
Step 3: Think about your result.
The equation is now balanced since there are equal numbers of atoms of each element on both sides of the equation.
Below are guidelines for writing and balancing chemical equation.
- Determine the correct chemical formulas for each reactant and product.
- Write the skeleton equation.
- Count the number of atoms of each element that appears as a reactant and as a product. If a polyatomic ion is unchanged on both sides of the equation, count it as a unit.
- Balance each element on at a time by placing coefficients in front of the formulas. No coefficient is written for a 1. It is best to begin by balancing elements that only appear in one formula on each side of the equation. NEVER change the subscripts in a chemical formula – you can only balance equations by using coefficients.
- Check each atom or polyatomic ion to be sure that they are equal on both sides of the equation.
- Make sure that all coefficients are in the lowest possible ratio. If necessary, reduce to the lowest ratio.
Aqueous solutions of lead(II) nitrate and sodium chloride are mixed. The products of the reaction are an aqueous solution of sodium nitrate and a solid precipitate of lead(II) chloride.
Step 1: Plan the problem.
Follow the steps for writing and balancing a chemical equation.
Step 2: Solve.
Write the skeleton equation with the correct formulas.
Pb(NO3)2(aq)+NaCl(aq)→NaNO3(aq)+PbCl2(s)
Count the number of each atom or polyatomic ion on both sides of the equation.
| reactants | products |
| 1 Pb atom | 1 Pb atom |
| 2 NO3- ions | 1 NO3- ions |
| 1 Na atom | 1 Na atom |
| 1 Cl atom | 2 Cl atoms |
The nitrate ions and the chlorine atoms are unbalanced. Start by placing a 2 in front of the NaCl. This increases the reactant counts to 2 Na atoms and 2 Cl atoms. Then place a 2 in front of the NaNO3. The result is:
Pb(NO3)2(aq)+2NaCl(aq)→2NaNO3(aq)+PbCl2(s)
The new count for each atom and polyatomic ion becomes:
| reactants | products |
| 1 Pb atom | 1 Pb atom |
| 2 NO3- ions | 2 NO3- ions |
| 2 Na atom | 2 Na atom |
| 2 Cl atoms | 2 Cl atoms |
Step 3: Think about your result.
The equation is now balanced since there are equal numbers of atoms of each element on both sides of the equation.
