5.4 To represent chemical change in the form of balanced equations Balancing Equations

All matter is made up of atoms Atoms combine in chemical reactions to form compound Each element has the same type of atoms

NaOH Na – 1 atom O - 1 atom H - 1 atom NH 4 NO 3 N - 2 atoms H - 4 atoms O - 3 atoms

C 3 H 5 (NO 3 ) 2 C - 3 atoms H - 5 atoms N - 2 atoms O - 6 atoms TRICKY

4 C 2 H 4 C - 8 atoms H - 16 atoms Watch out for the # in front! The number in front of the entire molecule tells how many molecules there is. In this example there are 4 molecules! C has 2 atoms but there are 4 molecules so that means there is 8 atoms all together

How many atoms are in each element for these compounds? H – 1 atom N – 1 atom O – 3 atoms H – 4 atom N – 4 atom O – 12 atoms Cu – 4 atom S – 2 atom 1. HNO HNO Cu 2 S 4. NH 4 NO Fe 2 SO 4 N– 2 atom H – 4 atom O – 3 atoms Fe– 4 atom S – 2 atom O – 8 atoms

H – 2 atom N – 2 atom O – 6 atoms C – 1 atom O – 5 atom S – 1 atoms Ca – 2 atom O – 2 atom H – 4 atoms 9. 4C 3 H 5 (NO 3 ) Fe 2 SO 4 C– 12 atom H – 20 atom N – 8 atoms O – 24 atoms Fe– 8 atom S – 4 atom O – 16 atoms 6. 2HNO 3 7. COSO Ca(OH 2 )

In all chemical reactions, the number of atoms of each element in the reactants will be equal to the number of atoms of each element in the products. 2H 2 + O 2 2H 2 O (balanced equation) Reactants = Products Hydrogen (H) = 4 atoms Oxygen (O) = 2 atoms Hydrogen (H) = 4 atoms Oxygen (O) = 2 atoms

0.5 L NaOH + HCl NaCl + H 2 O First list all the elements separately on each side Na = O = H = Cl = Reactants = Products Count all your atoms for each element 1 atom 1 atom 1 atom 1 atom 2 atoms 2 atoms 1 atom 1 atom YES… it is a balanced equation

0.5 L H = H = O = O = Reactants = Products First list all the elements separately on each side

0.5 L H = 2 atoms O = 2 atoms O = 1 atom Second, count the number of atoms for the reactants and # of atoms for the products for each element Reactants = Products These are not the same…..so this equation is NOT balanced!

0.5 L H = 2 atoms O = 2 atomsO = 1 atom NEVER EVER add a number directly into compound!!! (only in front!) The final balanced equation is Never Here! Add a number (co-efficient) in front of one or more of the molecules to make the equation balanced.

Fe 2 O 3 + C  CO 2 + Fe Reactants = Products Fe = O = C = 2 atoms 1 atom 3 atoms 2 atoms 1 atom 1 atom The final balanced equation is:

Al + CuCl 2  AlCl 3 + Cu Reactants = Products Al = Cu = Cl = 1 atom 1 atom 1 atom 1 atom 2 atoms 3 atoms The final balanced equation is:

Na 2 CO 3 + Ca(OH) 2  CaCO 3 + NaOH Reactants = Products Na = C = O =O = H = Ca =Ca = 2 atoms 1 atom 1 atom 1 atom 5 atoms 4 atoms 2 atoms1 atom 1 atom1 atom A solution of sodium carbonate (Na 2 CO 3 ) reacts with a solution of calcium hydroxide (Ca(OH) 2 ) to give precipitate of calcium carbonate (CaCO 3 ) and a solution of sodium hydroxide (NaOH). Write a balanced equation for this reaction

o When balancing equations o First list elements on each side o Second count atoms for each element o Add a number in front of molecule to balance the atoms o NEVER EVER add a number in between a molecule!!! (always put it in front)

 WORKSHEET # 11  Study guide, Module 3, page 38