Chapter 20 Oxidation-Reduction Reactions  What did you do yesterday? How many different ways could you describe the reactions?

Yesterday’s lab could be called...  Single replacement reactions  Metal reactivity reactions  AND.... Oxidation-Reduction too!!!  Anything else?????

What is REDOX??  A chemical reaction involving the transfer of electrons; one “species” gains electrons and another “species” loses electrons. OXIDATION The loss of electron(s)s The oxidation number of the species increases OIL – Oxidation is Loss REDUCTION The gain of electron(s) The oxidation number of the species decreases RIG – Reduction is Gain

Mg + Zn(NO 3 ) 2  Zn + Mg(NO 3 ) 2   1) Assign oxidation numbers   2) Determine what increased or decreased in oxidation number.   3) Determine what gained or lost electrons.   4) Determine the spectator ion.

Mg + Zn(NO 3 ) 2  Zn + Mg(NO 3 ) 2   1) Mg 0  Mg +2 and Zn +2  Zn 0   2) Mg increased; Zn decreased   3) Mg is oxidized; Zn is reduced  (NO 3 )  4) (NO 3 ) -1 is the spectator ion.

Try some others, but first determine if they would react!!   PbCl 4 + Al    AgCl + Au 

Writing half reactions  Figure out which side the electrons need to appear. If they are gained, they appear on the reactant side. If they are lost, they are added to the product side.   Zn e -  Zn 0   Mg 0  Mg e -

Ch. 11.3: Chemical Reactions Solubility Rules Writing Net Ionic Equations

Solubility Rules  Rules that help us predict which compounds will be soluble/insoluble

Solubility Rules 1. All group IA salts are soluble. 2. All ammonium salts are soluble. 3. All salts containing nitrate, acetate, chlorate, and perchlorate are soluble. 4. All salts are containing halides are soluble EXCEPT silver, mercury(I), and lead. 5. All sulfate salts are soluble EXCEPT barium, calcium, strontium, silver, mercury(I), and lead. 6. All salts containing carbonates, phosphates, and chromates are insoluble EXCEPT for rules #1 and #2. 7. All sulfide salts are insoluble EXCEPT for rules #1 and #2 and calcium, strontium, and barium. 8. All hydroxide salts are insoluble EXCEPT rules #1 and #2 and barium and strontium. ** Will be given for a test or quiz, no need to memorize!!

Is it Soluble?  Na 3 PO 4 Yes- (aq) Yes- (aq)  AgNO 3 Yes- (aq) Yes- (aq)  (NH 4 ) 2 SO 4 Yes- (aq) Yes- (aq)  Fe(CH 3 COO) 3 Yes- (aq) Yes- (aq)  BaCO 3 No- (s)  PbCl 2 No- (s)  Ca 3 (PO 4 ) 2 No- (s)  Ni(OH) 2 No- (s)

Precipitation Reactions  Remember that all ionic compounds are considered strong electrolytes dissociate completely in water dissociate completely in water  When two solutions are mixed, free ions are floating around  They collide together randomly  If an ionic compound forms that is insoluble in water, it is called a precipitation reaction

Precipitation Reactions

Types of Equations  molecular equation overall reaction overall reaction normal type we have been writing normal type we have been writing  complete ionic equation all strong electrolytes are broken into ions all strong electrolytes are broken into ions  net ionic equation all spectator ions are cancelled out all spectator ions are cancelled out only includes species active in chemical reaction only includes species active in chemical reaction

Types of Electrolytes  Break Apart (Strong) must be (aq) must be (aq) soluble ionic compounds soluble ionic compounds  Don’t break apart (weak/non) anything (g), (s), (l)

Write the net ionic equations  solution of strontium chloride is mixed with solution of potassium sulfate SrCl 2 (aq) + K 2 SO 4 (aq)  SrSO 4 (s) + 2KCl(aq) SrCl 2 (aq) + K 2 SO 4 (aq)  SrSO 4 (s) + 2KCl(aq)  complete ionic: Sr 2+ (aq) + 2Cl - (aq) +2K + (aq) + SO 4 2- (aq)  SrSO 4 (s) + 2K + (aq) + 2Cl - (aq) Sr 2+ (aq) + 2Cl - (aq) +2K + (aq) + SO 4 2- (aq)  SrSO 4 (s) + 2K + (aq) + 2Cl - (aq)  spectators: 2Cl - (aq) and 2K + (aq)  net ionic: Sr 2+ (aq) + SO 4 2- (aq)  SrSO 4 (s) Sr 2+ (aq) + SO 4 2- (aq)  SrSO 4 (s)

Write the net ionic equations  solution of sodium sulfide and solution of iron (II) nitrate are mixed Na 2 S(aq) + Fe(NO 3 ) 2 (aq)  Na 2 S(aq) + Fe(NO 3 ) 2 (aq)   complete ionic:  spectators:  net ionic:

Write the net ionic equations  solution of sodium sulfide and solution of iron (II) nitrate are mixed Na 2 S(aq) + Fe(NO 3 ) 2 (aq)  2NaNO 3 (aq) + FeS(s) Na 2 S(aq) + Fe(NO 3 ) 2 (aq)  2NaNO 3 (aq) + FeS(s)  complete ionic: 2Na + (aq) + S 2- (aq) + Fe 2+ (aq) + 2NO 3 - (aq)  2Na + (aq) + 2NO 3 - (aq) + FeS(s) 2Na + (aq) + S 2- (aq) + Fe 2+ (aq) + 2NO 3 - (aq)  2Na + (aq) + 2NO 3 - (aq) + FeS(s)  spectators: 2Na + (aq) and 2NO 3 - (aq)  net ionic: S 2- (aq) + Fe 2+ (aq)  FeS(s) S 2- (aq) + Fe 2+ (aq)  FeS(s)

Write the net ionic equations  Solution of aluminum chloride and solution of silver nitrate are mixed AlCl 3 (aq) + 3AgNO 3 (aq)  AlCl 3 (aq) + 3AgNO 3 (aq)   complete ionic:  spectators:  net ionic:

Write the net ionic equations  Solution of aluminum chloride and solution of silver nitrate are mixed AlCl 3 (aq) + 3AgNO 3 (aq)  3AgCl(s) + Al(NO 3 ) 3 (aq) AlCl 3 (aq) + 3AgNO 3 (aq)  3AgCl(s) + Al(NO 3 ) 3 (aq)  complete ionic: Al 3+ (aq) + 3Cl - (aq) + 3Ag + (aq) + 3NO 3 - (aq)  3AgCl(s) + Al 3+ (aq) + 3NO 3 - (aq) Al 3+ (aq) + 3Cl - (aq) + 3Ag + (aq) + 3NO 3 - (aq)  3AgCl(s) + Al 3+ (aq) + 3NO 3 - (aq)  spectators: Al 3+ (aq) and 3NO 3 - (aq)  net ionic: 3Cl - (aq) + 3Ag + (aq)  3AgCl(s) 3Cl - (aq) + 3Ag + (aq)  3AgCl(s) Cl - (aq) + Ag + (aq)  AgCl(s) Cl - (aq) + Ag + (aq)  AgCl(s)

Write the net ionic equations  Solution of sodium chloride and solution of potassium nitrate are mixed NaCl(aq) + KNO 3 (aq)  NaNO 3 (aq) + KCl(aq) NaCl(aq) + KNO 3 (aq)  NaNO 3 (aq) + KCl(aq)  complete ionic: Na + (aq) + Cl - (aq) + K + (aq) + NO 3 - (aq)  Na + (aq) + NO 3 - (aq) + K + (aq) + Cl - (aq) Na + (aq) + Cl - (aq) + K + (aq) + NO 3 - (aq)  Na + (aq) + NO 3 - (aq) + K + (aq) + Cl - (aq)  spectators: everything!  net ionic: nothing!

Precipitation Reactions  If no insoluble compound forms, no reaction has actually happened  It is just a solution with lots of free ions floating around  Spectator Ions free ions not involved in chemical reaction free ions not involved in chemical reaction

Tips for writing equations 1. Balance at the beginning should stay balanced the whole way through should stay balanced the whole way through may simplify at the end if necessary may simplify at the end if necessary 2. All ions should be (aq) – break apart for ionic equation 3. Keep symbols (i.e.- aq, s, l, g) written through entire process 4. Cancel out spectator ions and common ions on both sides for net ionic equation

In Conclusion  Remember net ionic equations identify what is ACTIVE in a chemical reaction  There are three steps that need to be identified to be able to write a complete net ionic equation  Make sure you understand each step!  Homework: 11.3 Practice Problems

 eOP2MfrDY