March 21, 2011 Please complete Monday Mystery Element! 1. Like most rare earth metals, used to make phosphors in TVs 2. Ferromagnetic (attracted to magnets) 3. Tarnishes slowly, oxide flakes off Now, please answer this question: Name the reactants in the following equation. Fe + Al(OH) 3  Fe(OH) 2 + Al

March 21, 2011 Please complete Monday Mystery Element! 1. Like most rare earth metals, used to make phosphors in TVs 2. Ferromagnetic (attracted to magnets) 3. Tarnishes slowly, oxide flakes off Now, please answer this question: Name the reactants in the following equation. Fe + Al(OH) 3  Fe(OH) 2 + Al GADOLINIUM (#64)

Today’s Agenda  Catalyst  Balancing Equations Day 1  Practice  Exit Question

Today’s Objectives  SWBAT apply law of conservation of mass to chemical reactions by balancing chemical equations.

Whiteboard Practice  How many total atoms of each element are in these compounds? AlCl 3 : Al = ? Cl = ? H 2 O: H = ? O = ? H 2 O 2 : H = ? O = ? KCl: K = ? Cl = ? Be 3 S 2 : Be = ? S = ? NH 4 NO 3 : N = ? H = ? O = ?

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

 What is a coefficient? GOOD QUESTION!

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

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

How many of each atom do we have now? 7 AlCl 3 4 H 2 O 6 H 2 O 2 5 KCl 2 Be 3 S 2 4 (NH 4 )NO 3

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

L-C-M!!!  Key Point #2: Chemical reactions MUST follow the Law of Conservation of Matter. What is the LCM?  Matter cannot be created or destroyed.  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 H 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!

Balancing with Polyatomic Ions  What if you have some polyatomic ions?  WHAT will you do??  Key Point #3: When balancing equations that involve polyatomic ions, keep them together!

Work it out…  H 3 PO 4 + ____ KOH  ____ K 3 PO 4 + ____ H 2 O  Which polyatomics are we using?  PO 4 – phosphate  OH – hydroxide  Where is the OH on the other side?  It’s OK – rewrite H 2 O as HOH – Trust me!

Your turn 1. HCl + NaOH  NaCl + H 2 O 2. NaOH + H 2 CO 3  Na 2 CO 3 + H 2 O 3. Al(OH) 3 + H 2 CO 3  Al 2 (CO 3 ) 3 + H 2 O

Balancing with diatomics…  Key Point #4: Sometimes with diatomics, you must be a little tricky.  C 4 H 10 + O 2  CO 2 + H 2 O

Diatomics  If you reach the point in a balance problem where everything is balanced except the diatomic atom...  You can only get even numbers with diatomics…  2 O 2 = 4 O atoms  3 O 2 = 6 O atoms  And sometimes the other side is odd  Use a fraction, then multiply by 2

Example: Work it out… C 4 H 10 + O 2  CO 2 + H 2 O

Your Turn… 1. C 6 H 6 + O 2  CO 2 + H 2 O 2. C 10 H 22 + O 2  CO 2 + H 2 O

Exit Question  Balance the following equations: 1. KClO 3 ---> KCl + O 2 2. S 8 + O 2 ---> SO 3