# reactant entities are on left side and change into

## Presentation on theme: "reactant entities are on left side and change into"— Presentation transcript:

Chemical equation the symbolic representation of a chemical reaction (process) wherein the
reactant entities are on left side and change into product entities on right-hand side

Chemical Equation Symbols
The arrow  can be read as “yields” or “produces” The + sign reads as “and” or “plus”

Chemical Equation Symbols
The arrow  can be read as “yields” or “produces” Coefficients are the numbers in front of the formulas Coefficients can be changed to balance chemical equations Subscripts tell us how many atoms or molecules we have NEVER change subscripts when balancing chem. equations

Balancing Equations like solving a puzzle
Br2 + Al  Al2Br6 (not balanced) Balance using coefficients

Balancing Equations Reactants  Products O2 + H2  H2O

Balancing Equations Reactants  Products
O2 + H2  H2O but this equation is not balanced why not?

Balancing Equations Conservation of Mass- Mass and/or Atoms are not Created or Destroyed during a chemical reaction. There must be the Same number of atoms on each side of the equation to balance the chemical equation.

Steps to Balance Chemical Equations
1. Write unbalanced equation. 2. Count # atoms on each side. 3. Add coefficients to make #s of atoms equal. Coefficient  subscript = # of atoms 4. If necessary reduce coefficients to lowest possible ratio (never change subscripts) Update and Double check atom balance!!!

Balancing Equations Step 1. Write unbalanced equation O2 + H2  H2O

Balancing Equations Step 2. Count # of atoms on each side
O2 + H2  H2O O = = 1 H = H = 2

Balancing Equations 3. Add coefficients to make # of atoms = on each side O2 + H2  H2O O = = 1 H = H = 2

Balancing Equations 3. Add coefficients to make # of atoms = on each side O H2  2 H2O O = = 2 H = H = 4

Balancing Equations 4. If necessary find lowest ratio (never change subscripts) O H2  2 H2O O = = 2 H = H = 4

Balancing Equations 5. Update and double check work O2 + 2 H2  2 H2O

Balancing Steps Al + CuCl2  Cu + AlCl3
1. Write the unbalanced equation. Al CuCl2  Cu AlCl3

Balancing Steps 1 Al 1 1 Cu 1 2 Cl 3 1. Write the unbalanced equation.
2. Count atoms on each side. Al CuCl2  Cu AlCl3 Al 1 Cu Cl

Coefficient  subscript = # of atoms
Balancing Steps 1. Write the unbalanced equation. 2. Count atoms on each side. 3. Add coefficients to make #s equal. Coefficient  subscript = # of atoms Al CuCl2  Cu AlCl3 Al 1 Cu Cl

Coefficient  subscript = # of atoms
Balancing Steps 1. Write the unbalanced equation. 2. Count atoms on each side. 3. Add coefficients to make #s equal. Coefficient  subscript = # of atoms Al CuCl2  Cu AlCl3 Al 3 Cu Cl

Coefficient  subscript = # of atoms
Balancing Steps 1. Write the unbalanced equation. 2. Count atoms on each side. 3. Add coefficients to make #s equal. Coefficient  subscript = # of atoms 2 Al CuCl2  3 Cu AlCl3 Al 3 Cu Cl

Coefficient  subscript = # of atoms
Balancing Steps 1. Write the unbalanced equation. 2. Count atoms on each side. 3. Add coefficients to make #s equal. Coefficient  subscript = # of atoms 4. Reduce coefficients to lowest possible ratio, if necessary. 5. Double check atom balance!!!

Helpful Tips Balance one element at a time. Balance most complicated compound first! Update ALL atom counts after adding a coefficient. Balance (polyatomic ions) as (single units). “1 SO4” instead of “1 S” and “4 O” Balance most complicated compound first, balance oxygen and hydrogen last (MINOH metals, ions, non-metals, oxygen, hydrogen) Ask yourself this question what am I forced to do to balance the equation???

Examples ____ Mg ____ O2  ____ MgO

Examples 2 Mg O2  2 MgO

Examples ____ Al ____ S  ____ Al2S3

Examples 2 Al S  Al2S3 ____ C3H8 +____ O2  ____ CO2 + ____ H2O

Examples 2 Al S  Al2S3 C3H8 + 5 O2  3 CO2 + 4 H2O

More Examples ___ Al +____ H2SO4  ____Al2(SO4)3 +____ H2

More Examples 2 Al + 3 H2SO4  Al2(SO4) H2

Helpful Tips Balance one element at a time.
Update ALL atom counts after adding a coefficient. Balance (polyatomic ions) as (single units). “1 SO4” instead of “1 S” and “4 O” Balance most complicated compound first, balance oxygen and hydrogen last Ask yourself this question what am I forced to do to balance the equation???