2NaCl + Ca₂O => Na₂O + CaCl₂ is the right equation for when sodium chloride reacts with calcium oxide, it will form sodium oxide and calcium chloride.
This is a double displacement reaction. The compounds in the reactants and products are both ionic because there are two metals and two non-metals.
The formula for each compound is correct because each of the number of atoms is the same as the charge of its bonded element.
The equation is also balanced. The number of elements in the reactants and products are the same. (Each side has 2 sodium, 2 chloride, 2 calcium and 1 oxygen).
Explanation:
Consider if a) the elements in the compounds are correct, b) the compound formulas are correct, and c) the equation is balanced.
a) What is formed when sodium chloride reacts with calcium oxide:
The products are not H2O and CO2 (combustion) and the reactants are not an acid and a base (neutralization), it is double displacement. This means each element will switch partners.
Compounds can only be covalent (non-metal + non-metal) or ionic (metal + non-metal). Since there are two metals (Na and Ca) in the reactants, the new compounds formed can only be ionic. They will form new non-metal bonds with O and Cl. Therefore sodium bonds with oxygen, calcium bonds with chloride.
b) Ensure the formulas are correct for each compound
First, write out the element ions symbols in a compound. The number of atoms an element gets is the charge of its partner.
REACTANTS
sodium chloride
Na⁺ and Cl⁻
NaCl (You do not need to write 1 for atoms)
calcium oxide
Ca⁺ and O²⁻
Ca₂O (oxygen's charge of 2 becomes number of calcium atoms)
PRODUCTS
sodium and oxygen
Na⁺ and O²⁻ (If the charge does not have a number, it is 1)
Na₂ O₁ (You do not need to write the one)
Na₂O
calcium and chloride
Ca²⁺ and Cl⁻
Ca₁Cl₂ (You do not need to write the 1)
CaCl₂
Put the formulas into the equation. Before its balanced, its called a skeleton equation.
NaCl + Ca₂O => Na₂O + CaCl₂
To check for balance, count the number of atoms on both sides for each element.
Reactants Products
Na 1 Na 2
Cl 1 Cl 2
Ca 2 Ca 1
O 1 O 1
The number of each element should be the same on both sides. Write in coefficients to make each side have the same number of elements. Since there are not enough Cl atoms in reactants, give it a coefficient.
Recount the number of atoms.
2NaCl + Ca₂O => Na₂O + CaCl₂
Reactants Products
Na 2 Na 2
Cl 2 Cl 2
Ca 2 Ca 1
O 1 O 1
The equation is now balanced.
