Balancing Equations and Types of Equations Day 9

Classifying Reactions Synthesis: reactions make larger molecules A + B  AB 2. Decomposition: Breaks compounds apart AB A + B 3. Single-replacement: elements trade place XA + B  BA + X 4. Double-replacement: exchange of ions between two compounds AX + BY AY + BX

Chemical Equations To write a correct chem. equation, the law of conservation of mass must be taken into account. This means…same numbers of each type of atom on each side of the equation

Balancing Chem. Equations Balancing of chem. equations is done by adding coefficients (number in front of the element or compound) Al + S Al2S3 Not Balanced 2Al + 3S Al2S3 Balanced

Never…. Never change a subscript to balance an equation. If you change the formula you are describing a different reaction. H2O is a different compound than H2O2 Never put a coefficient in the middle of a formula 2 NaCl is okay, Na2Cl is not.

Learning Check E4 Fe3O4 + 4 H2 3 Fe + 4 H2O A. Number of H atoms in 4 H2O B. Number of O atoms in 4 H2O C. Number of Fe atoms in Fe3O4

Steps in Balancing An Equation Fe3O4 + H2 Fe + H2O Fe: Fe3O4 + H2 3 Fe + H2O O: Fe3O4 + H2 3 Fe + 4 H2O H: Fe3O4 + 4 H2 3 Fe + 4 H2O

Balance each equation. Add coefficients A. Mg + N2 Mg3N2 B. Al + Cl2 AlCl3

Solutions A. 3 Mg + N2 Mg3N2 B. 2 Al + 3 Cl2 2 AlCl3