1. “Chemical Reactions”

2. Chemical Reactions
Chemical reactions, or chemical changes, happen when the atoms in one or more chemicals split up and join together in new ways. For example, hydrogen can react with oxygen :
hydrogen + oxygen
water
Before the reaction the oxygen atoms go round in pairs, and the hydrogen atoms go round in pairs. When they react we get two new molecules, of the compound water.
Each of these molecules has three atoms, two hydrogen atoms joined to one oxygen atom.
We can write this as H2O.

3. All chemical reactions…
have two parts:
Reactants - the substances you start with
Products- the substances you end up with
The reactants turn into the products.
Reactants ® Products

4. Chemical Changes
Products
Reactants

5. In a chemical reaction Atoms aren’t created or destroyed.
A reaction can be described several ways:
1. In a sentence (every item is a word)
Copper reacts with chlorine to form copper (II) chloride.
2. In a word equation (some symbols used)
Copper + chlorine ® copper (II) chloride

6. Symbols in equations
the arrow separates the reactants from the products
Read as “reacts to form” or yields
The plus sign = “and”
(s) after the formula = solid: AgCl(s)
(g) after the formula = gas: CO2(g)
(l) after the formula = liquid: H2O(l)

7. Symbols used in equations
(aq) after the formula = dissolved in water, an aqueous solution: NaCl(aq) is a salt water solution

8. 3. The Chemical Equation
Uses formulas and symbols to describe a reaction
All chemical equations are a description that describe reactions.

9. Write an equation for:
Solid iron (III) sulfide reacts with gaseous hydrogen chloride to form iron (III) chloride and hydrogen sulfide gases.
Fe2S3(s) + HCl(g) FeCl3(g) + H2S(g)
2. Solutions of ammonium hydroxide and silver chloride form solid silver hydroxide and ammonium chloride solution.
NH4OH(aq) + AgCl(aq) AgOH(s) + NH4Cl(aq)

10. Now, read these: Fe(s) + O2(g) ® Fe2O3(s) NO2 (g) N2(g) + O2(g)
Cu(s) + AgNO3(aq) ® Ag(s) + Cu(NO3)2(aq)
NO2 (g) N2(g) + O2(g)

11. Types of Chemical Reactions
There are five general types of reactions.
This will help to predict the products of the five general types of reactions.
Combination/Synthesis
Decomposition
Single displacement
Double displacement
Combustion

12. The reaction of sugar with concentrated sulfuric acid.

13. #1 – Combination/Synthesis Reactions
Combine = put together
2 substances combine to make one compound.(one product only)
A + B = AB
Ca +O2 ® CaO
SO3 + H2O ® H2SO4

14. +

15. #2 - Decomposition Reactions
decompose = fall apart
one reactant breaks apart into two or more elements or compounds.
AB= A + B
NaCl Na + Cl2
CaCO CaO + CO2
Note that energy (heat, sunlight, electricity, etc.) is usually required

16. #2 - Decomposition Reactions

18. #3 - Single Displacement
One element replaces another
Reactants must be an element and a compound.
Products will be a different element and a different compound.
A + BC= AC + B or BA + C
Na + KCl ® K + NaCl (Na replaces K since one is metal and one is metal ion)
F2 + LiCl ®LiF + Cl2 (F replaces Cl since one is a non metal and the other is a non-metal ion)

19. #3 - Single Displacement+

20. +

21. #3 Single Displacement Practice:
Fe + CuSO4 ®
Pb + KCl ®
Al + HCl ®

22. Consult the activity series of metals
If metal alone in bce is ABOVE metal in ionic compound, it will REPLACE the cation. Electrons will be transferred and a new metal and ionic compound will form.
Li can replace K in the equation
KCl + Li = LiCl + K
Ca cannot replace Ba
Ca + BaCl2 = no reaction
Top 5 (Li K Ba Ca Na) react in water replaces ONE hydrogen in HOH
2K + HOH= 2KOH + H2
Top 12 (above H) react with acids
2Al + 6HCl = 2AlCl3 + 3H2 Li K Ba Ca Na Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au

23. Consult the activity series for non-metals
If non metal alone in bce is ABOVE non-metal in ionic compound, it will REPLACE the anion. Electrons will be transferred and a new metal and ionic compound will form.
F can replace Cl in the equation
2KCl + F2 = 2KF + Cl2
Br cannot replace Cl
Br2 + BaCl2 = no reaction F Cl Br I

24. #4 - Double Displacement
Two things replace each other. (usually aqueous)
Reactants must be two ionic compounds.
AB + CD = CB + AD
NaOH + FeCl3 ®
The positive ions change place.
NaOH + FeCl3 ® Fe+3 OH- + Na+1 Cl-1
NaOH + FeCl3 ® Fe(OH)3 + NaCl
Formulas of products are based on octets for all or crisscross rule not on how many in reactants
Balance after products predicted
3NaOH + FeCl3 ® Fe(OH)3 + 3NaCl

25. Double Displacement
Shania Twain/ Mutt Lange + Marie Ann Thiebaud/Frederic Thebaud = Shania Twain/Fredeic Thiebaud + Marie Anne Thiebaud/Mutt Lange

26. + CD AB

27. + CB AD

28. Complete and balance:
assume all of the following reactions actually take place:
CaCl2 + NaOH ®
CuCl2 + K2S ®
KOH + Fe(NO3)3 ®
(NH4)2SO4 + BaF2 ®

29. How to recognize which type
Look at the reactants:
E + E = C Synthesis
C = __+__ Decomposition
E + C=E + C Single displacement
C + C= Double displacement

30. Practice Examples: H2 + O2 ® H2O ® Zn + H2SO4 ® HgO ® KBr +Cl2 ®
AgNO3 + NaCl ®
Mg(OH)2 + H2SO3 ®

31. #5 - Combustion Means “add oxygen”
Normally, a compound composed of only C, H, (and maybe O) is reacted with oxygen – usually called “burning”
If the combustion is complete, the products will be CO2 and H2O water.
If the combustion is incomplete, the products will be CO (or possibly just C) and H2O water.
CxHy + O2 = CO2 + H20
C8H O2 = 8CO2 + 9H20
C + E = C + C