1. Product or Reactant?
• H2SO4 + BaCl2
1. BaCl2
Reactant
Product
2. HCl
3. BaSO4
4. H2SO4
Product
Reactant
2HCl + BaSO4

2. Review
Chemical Reactions
Law of Conservation of
Matter

3. 1. Synthesis Reactions
Combining of several
simple substances to
form a more complicated
substance

4. Synthesis Reactions
A + B  AB
A = element
B = element
AB = compound

5. Synthesis Reactions
2Mg + O  2MgO
2
Magnesium (A) + Oxygen (B)
Magnesium oxide (AB)

6. 2. Decomposition Reactions
The break down of a
compound into simpler
substances
AB  A + B
Opposite of synthesis

7. Decomposition Reactions
2H O 
2
2H2 + O2
Done by electrolysis

8. 3. Single Replacement
A free element takes the place
of, or replaces, another element
Takes place between an
element and a compound

9. Single Replacement
A + BC  AC + B
A – free element
BC - compound
AC – new compound
B - new free element

10. Single Replacement
Zn + 2HCl 
ZnCl2 + H2
Hydrogen is set free

11. 4. Double Replacement
 Two elements in two different
compounds switch places with
each other
 Takes place between two
compounds
 Two new compounds form

12. Double Replacement
AB + CD  AD + CB
AB – compound 1
CD – compound 2
AD – new compound 1
CB – new compound 2

13. Double Replacement
 Na(OH) + HCl
 NaCl +
H(OH)
 (OH) and Cl change places
 2 new compounds form
 NaCl and H O
2

14. These reactions can be…
ExothermicHeat is given
off
It feels hot!

15. These reactions can be…
EndothermicHeat is
absorbed
It feels cold!