Balancing Equations March, *10 3  Objective:  SWBAT apply law of conservation of mass to chemical reactions by balancing!  Catalyst:  Name the reactants in this equation. Fe + Al(OH) 3  Fe(OH) 2 _ + Al  Name the products in this equation. 2H 2 + O 2  2H 2 O

Agenda  Catalyst  Go over test!  Balancing Equations  Practice  Exit Question

Whiteboard Practice  How many atoms are in these compounds?  AlCl 3  H 2 O  H 2 O 2  KCl  Be 3 S 2  NH 4 NO 3

Balancing equations RULES!  Key Point #1: When balancing equations, Never, Never, NEVER change subscripts, only coefficients!

Yo, Mr. Jhaveri  What is a coefficient?  GOOD QUESTION!

Coefficient  A coefficient is a whole number comes in front of the compound, never in the middle!  You multiply the coefficient to all the numbers in the compound 2AlCl 3

Do you get it?  3AlCl 3  How many atoms of each element do they have?  3 Aluminum’s  9 Chlorine’s

Whiteboard Practice  2AlCl 3  4H 2 O  6H 2 O 2  5KCl  2Be 3 S 2  4(NH 4 ) 3 NO 3

Why is the top equation wrong? (5 minutes) – You figure it out  We never want to leave an equation written like this…  H 2 + O 2  H 2 O  We want to have it like this…  2H 2 + O 2  2H 2 O  WHY???

L-C-M!!!  Key Point #2:  Chemical reactions MUST follow the law of conservation of mass.  What was that LCM again?  If 3 carbons are in the reactants of a reaction, then there darn well better be 3 carbons in the products of a reaction.

Balancing Chemical Reactions H 2 + O 2  H 2 O __H__ __O__ Write down elements.

Balancing Chemical Reactions H 2 + O 2  H 2 O __H__ __O__ How many are there?

Balancing Chemical Reactions H 2 + O 2  H 2 O _2_H_2_ __O__ How many are there?

Balancing Chemical Reactions H 2 + O 2  H 2 O _2_H_2_ _2_O_1_ How many are there?

Balancing Chemical Reactions Try These: N 2 + H 2  NH 3 P 4 O 10 + H 2 O  H 3 PO 4 Ca 3 P 2 + H 2 O  Ca(OH) 2 + PH 3

Balancing Chemical Reactions Try These: N 2 + 3H 2  2NH 3 P 4 O 10 + H 2 O  H 3 PO 4 Ca 3 P 2 + H 2 O  Ca(OH) 2 + PH 3

Balancing Chemical Reactions Try These: N 2 + 3H 2  2NH 3 P 4 O H 2 O  4H 3 PO 4 Ca 3 P 2 + H 2 O  Ca(OH) 2 + PH 3

Balancing Chemical Reactions Try These: N 2 + 3H 2  2NH 3 P 4 O H 2 O  4H 3 PO 4 Ca 3 P 2 + 6H 2 O  3Ca(OH) 2 + 2PH 3

Independent Practice  Worksheet!

Exit Question  Balance the following equations:  KClO 3 ---> KCl + O 2  S 8 + O 2 ---> SO 3