Post on 29-Dec-2015
Recall
Reactant + reactant product
Word equation
Sodium + chlorine Sodium chloride
Chemical equation
Na + Cl NaCl
Synthesis Reactions
Two substances (elements) combine and form a compound
A + B C– Reactant + reactant product– Carbon + oxygen Carbon dioxide
– C + O2 CO2
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
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
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
Combustion Reactions
A substance reacts with oxygen to produce carbon dioxide and water
X + O2 CO2 + H2O
Reactivity A more reactive element can displace a
less reactive element in a single displacement reaction
Applies to Alkali metals (Group 1)
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
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
RULES FOR COUNTING ATOMS
1. SUBSCRIPTS only refer to the atom that they are BEHIND. For example…
H2SThere are TWO atoms of HYDROGEN and only ONE atom of SULFUR.
COEFFICIENTS
2. 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!
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
LET’S PRACTICE!LET’S PRACTICE!
MgCl2
Atoms of Magnesium:
Atoms of Chlorine:
1
2
Al2S3
Atoms of Aluminum:
Atoms of Sulfur:
2
3
PRACTICEPRACTICE
H2SO4
Atoms of Hydrogen:Atoms of Sulfur:Atoms of Oxygen:
21
CH3OHAtoms of Carbon:
Atoms of Hydrogen:
Atoms of Oxygen:
14
4
1
THIS COULD BE A LITTLE THIS COULD BE A LITTLE TRICKY…TRICKY…
Ca3(PO4)2 Atoms of Calcium:Atoms of Phosphorus:Atoms of Oxygen:
32
Al2(SO4)3
Atoms of Aluminum:
Atoms of Sulfur:
Atoms of Oxygen:
23
8
12