1. Unit 6: Chemical Reactions

2. What is a chemical reaction?
One or more substances change into one or more new substances whose chemical and physical properties differ from the original substances
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3. Signs of a Chemical Reaction

4. Chemical Reaction or Not?

5. Reading Chemical Equations
Chemical equation: shows the chemical formulas and the relative amounts of all reactants and products separated by an arrow
CH4 + O2  H20 + CO2
Products
Reactants

6. What is all the symbolism?
Meaning of the arrows
" " symbol is used to denote a net forward reaction.
" " symbol is used to denote a reaction in both directions.
" " symbol is used to denote an equilibrium.
Nature of the substrates
aq = aqueous
l = liquid
s = solid
g = gas

7. Decoding Equations: What do the following equations mean?
H2CO3(aq)  →   H2O(l) + CO2(g)
Aqueous carbonic acid yields water and carbon dioxide gas
NH4OH(aq)  →   NH3(g) + H2O(l)
Aqueous ammonium hydroxide yields ammonia gas + water

8. What is all the symbolism?
More arrows with special features

9. Classifying chemical reactions
Classifying chemical reactions allows us to be able to predict the products when only given the reactants
There are 5 main ones:
Combustion
Synthesis
Decomposition
Single displacement
Double-displacement

10. Types of Chemical Reactions
Combustion: the reaction of a carbon-based compound with oxygen
Carbon based compound + oxygen  carbon dioxide + water
i.e.
CH4 + O2  H20 + CO2
What’s a fire and why does it… what’s the word? Burn…

11. Types of Chemical Reactions
2. Synthesis: a single compound forms two or more reactants
A + B  AB
i.e. C + O2  CO2
i.e. CaO + H2O  Ca(OH)2

12. Types of Reactions
Decomposition: a single compound breaks down into two or more elements or simpler compounds
AB  A + B
i.e. 2H2O (l)  2H2 (g) + O2 (g)

13. Types of Reactions Displacement
Single Displacement: a single element reacts with a compound and displaces another element from the compound
A + BC  B + AC
i.e. 2Al (s) + 3CuCl2 (aq)  2AlCl3 (aq) + 3Cu (s)
Double Displacement: two compounds appear to exchange ions and form new compounds
AB + CD  AD + CB
i.e. HCl (aq) + NaOH (aq)  HOH (l) + NaCl (aq)

14. Practice: which type of reaction does each chemical equation represent?
Ca(OH)2 + Al2(SO4)3  CaSO4 + Al(OH)3 Mg + Fe2O3  Fe + MgO C2H4 + O2  CO2 + H2O PbSO4  PbSO3 + O2 NH3 + I2  N2I6 + H2 H2O + SO3  H2SO4
HW: finish
Have a WS where they have to figure out which equation is which
Next day, do a lesson on determining the products given that it is a certain kind of reaction

15. Predicting the Products of Single Displacement Reactions
Elements will only displace an element that is less reactive than itself
To determine which elements are most reactive, chemists use an activity series

16. Practice Will magnesium react with lead (II) nitrate?
Write out the chemical equation
Mg + Pb(NO3)2 
Identify the reactants
Will Mg displace Pb?
3. Check the activity series
Mg is above Pb ergo the rxn
will take place
Write the products
Mg + Pb(NO3)2  Pb + Mg(NO3)2

17. More practice Will copper react with lead (II) nitrate?
Write out the chemical equation
Cu + Pb(NO3)2 
Identify the reactants
Will Cu displace Pb?
3. Check the activity series
Cu is below Pb ergo the rxn
WILL NOT TAKE PLACE
Write the products
Mg + Pb(NO3)2  No reaction

18. Predicting whether or not chemicals will react in displacement reactions
In order for a double displacement to occur, one of the products must be a solid precipitate, a gas, or a molecular compound
We will be focusing on precipitation reactions, and predicting whether or not there will be a precipitate.
Then show an example of a precipitation rxn

19. Precipitation Reaction
In order for a precipitation reaction to occur, at least one of the products must be a solid (precipitate)
Therefore, we use solubility rules to determine what is soluble in water (aq) and what is not (s).

20. Compounds containing these ions are soluble in water:
Group 1A elements (Li, Na, K, Rb, Cs, Fr)
Exceptions: LiF
Ammonium salts (NH4+)
Exceptions: none
Nitrate (NO3-), chlorate (ClO3-), and perchlorate (ClO4-)
Acetate (CH3COO- or C2H3O2-, sometimes abbreviated as Oac-)
Exceptions: Fe3+
Chlorides (Cl-), bromides (Br-), and iodides (I-)
Exceptions: Ag+, Pb2+, and Hg22+
Sulfate ( SO42-)
Exceptions: Ba2+, Sr2+, Ca2+, Pb2+, Hg22+, and Hg2+, Ca2+ and Ag+
Compounds containing these ions are insoluble in water
Hydroxide (OH-)
Exceptions: Group IA (alkali metals), Ba2+, Ca2+, and Sr2+.
Sulfide (S2-)
Exceptions: Groups I-A and II-A (alkali metals and alkali earth metals)
Sulfites (SO32-), carbonates (CO32-), chromates (CrO42-), and phosphates (PO43-)
Exceptions: NH4+ and Group I-A (alkali metals)
Oxides (O2-)
Exceptions: Group 1, Ca2+, Sr2+, and Ba2+

21. Group Work Groups Group 1 Alameen Gulberlyne Shaquo Group 4 Ruvym Klea
Brandon
Group 7
Gheed
Gabi
Son
Group 10
Laura
Kim
Marcus
Group 8
Esther
Edward
Deana
Brandy
Group 2
Calvin
Riya
Pascal
Brandy
Group 5
Justine
Jeneiva
Huy Trieu
Group 9
Daniela
Daisha
Ciera
Will
Group 3
Pam
Niyati
Asmar
Group 6
Huy To
Huiwen
Firuza

22. Example Will ammonium carbonate react with magnesium chloride?
Write out the chemical equation
(NH4)2CO3 (l)+ MgCl2 (l) ???
Figure out the products
(NH4)2CO3 (l)+ MgCl2 (l) NH4Cl + MgCO3
Figure out the solubility of the products using the solubility rules
NH4Cl is soluble because all compounds with ammonium in them are soluble
MgCO3 is insoluble because all (almost) all compounds with CO3 in them are insoluble
4. Determine whether the reaction takes place
YES!

23. Another example Will iron (III) nitrate react with magnesium acetate?
Write out the chemical equation
Fe(NO3)3 + Mg(C2H3O2)2 ???
Figure out the products
Fe(NO3)3 + Mg(C2H3O2)2 Fe (C2H3O2)3 + Mg(NO3)2
Figure out the solubility of the products using the solubility rules
Mg(NO3)2 is soluble because all compounds with nitrate in them are soluble
Fe (C2H3O2)3 is insoluble because though (almost) all compounds with C2H3O2 in them are soluble, it is insoluble when its bonded with Fe (the exception)
4. Determine whether the reaction takes place
YES!

24. Homework Problem Review
lithium carbonate + chromium (III) nitrate →

25. Homework Problem Review
Na3PO4 + Ba(NO3)2 →

26. Homework Problem Review
AgBr + BaI2 →

27. Homework Problem Review
silver chlorate + potassium chloride →

28. Homework Problem Review
lead (II) chlorate + magnesium chloride →