1. Types of Chemical Reactions & Counting Atoms
Grade 10 Chemistry

2. Recall Reactant + reactant  product Word equation
Sodium + chlorine  Sodium chloride
Chemical equation
Na + Cl  NaCl

3. Types of Reactions Synthesis Decomposition Single-displacement
Double-displacement
Combustion

4. Synthesis Reactions
Two substances (elements) combine and form a compound
A + B  C
Reactant + reactant  product
Carbon + oxygen  Carbon dioxide
C + O2  CO2

5. Decomposition Reactions
Compound breaks down into two elements (or simpler compounds)
Reverse of synthesis
C  A + B
Reactant  product + product
Water  hydrogen + oxygen
2 H2O  2H2 + O2

6. Single-displacement Reactions
One element replaces another element in a compound
Metal replaces a metal
Non-metal replaces a non-metal
Get a new element and a different compound
A + BC  AC + B
zinc + hydrochloric acid  zinc chloride + hydrogen

7. Double-displacement Reactions
Ions from two compounds change places
Metal replaces a metal
Non-metal replaces a non-metal
AB+ CD  AD + CB
Sodium chloride + silver fluoride Sodium fluoride + silver chloride

8. Combustion Reactions
A substance reacts with oxygen to produce carbon dioxide and water
X + O2  CO2 + H2O

9. Reactivity
Reactive - will readily take part in chemical reactions

10. Reactivity
A more reactive element can displace a less reactive element in a single displacement reaction
Applies to Alkali metals (Group 1)

11. Reactivity Series

12. Reactivity Example Single displacement reaction:
Copper is more reactive than silver
Cu + AgNO3  CuNO3 + Ag
The copper displaces the silver in the compound silver nitrate

13. Reactivity Example Continued
Single displacement reaction:
Silver is less reactive than copper
Ag + CuNO3  AgNO3 + Cu
The silver cannot displace the copper because it is less reactive. Chemical reaction does not occur

14. Counting Atoms

15. RULES FOR COUNTING ATOMS
SUBSCRIPTS only refer to the atom that they are BEHIND. For example…
H2S
There are TWO atoms of HYDROGEN and only ONE atom of SULFUR.

16. COEFFICIENTS
COEFFICIENTS apply to the entire compound. You MULTIPLY the coefficients and SUBSCRIPTS.
2 H2S
ATOMS OF HYDROGEN:
ATOMS OF SULFUR: 4 2
IF THERE ISN’T A SUBSCRIPT BEHIND AN ELEMENT, ASSUME THERE IS ONLY ONE ATOM OF THAT ELEMENT!

17. PARENTHESES
3. If elements or compounds are inside of PARENTHESES, then the SUBSCRIPT behind the parentheses applies to everything inside the parentheses.
Ba(OH)2
ATOMS OF BARIUM:
ATOMS OF OXYGEN:
ATOMS OF HYDROGEN: 1 2 2

18. LET’S PRACTICE! MgCl2 Atoms of Magnesium: Atoms of Chlorine: 1 2 Al2S3
Atoms of Aluminum:
Atoms of Sulfur: 2 3

19. PRACTICE 2 1 4 CH3OH 1 4 1 H2SO4 Atoms of Hydrogen: Atoms of Sulfur:
Atoms of Oxygen: 2 1 4
CH3OH
Atoms of Carbon:
Atoms of Hydrogen:
Atoms of Oxygen: 1 4 1

20. THIS COULD BE A LITTLE TRICKY…
Ca3(PO4)2
Atoms of Calcium:
Atoms of Phosphorus:
Atoms of Oxygen: 3 2 8
Al2(SO4)3
Atoms of Aluminum:
Atoms of Sulfur:
Atoms of Oxygen: 2 3 12

21. Homework
Counting atoms worksheet
Predict products of worksheet