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Chemical reactions
Remember indications of a chemical change energy change Color change Precipitate formed Gas given off
What is energy?
Anything that is not matter and can cause a change in matter
Examples: Heat Sound light
Symbols to know
yields or reacts to form+ plus or and(s) solid(l) liquid(g) gas(aq) dissolved in watercatalyst is written on
yields signHeat is a triangle on yields sign
Remember
Ionic compounds are usually solids (s)(but they can be dissolved in water)
All acids are dissolved in water (aq) Metals are solid except Hg Br2 is a liquid
Magnesium metal and sodium chloride dissolved in water react to form magnesium chloride dissolved in water and sodium metal
Try these!
Solid magnesium reacts with oxygen in the air to form solid magnesium oxide.
Bubbles of hydrogen gas and aqueous zinc sulfate are produced when zinc metal is added to sulfuric acid
Diatomic molecules
H2 N2 O2 F2
Cl2 Br2
I2
matter cannot be created nor destroyed (its conserved).
number of atoms reacted equals number of atoms produced
take an atom inventory
Law of Conservation of
Matter
Rules for Balancing Equations
1.Write reactants on left, products on right
2 Write correct formulas3. Take an atom inventory4. Balance the number of atoms by
placing a coefficient in front of the formula(DON’T CHANGE SUBSCRIPTS)
5. Repeat until all atoms are balanced6. Put coefficients in lowest terms
Practice
Balance and write the words:
Br2(l) + NaI(aq) NaBr(aq) + I2(s)
Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)
Practice
Mercury metal is produced by heating a mixture of mercury(II)sulfide and calcium oxide. Other products are calcium sulfide and calcium sulfate.
Types of Chemical reactions
Combination(synthesis)A + B AB
DecompositionAB A + B
Single replacementA + BX AX + B
Double Replacement AX + BYAY + BX Combustion
HxCy + O2 CO2 + H2O
Combination(synthesis)
Mg + O2 MgO
Sodium and chlorine react to form
Iron and oxygen react to form iron (III) product
Decomposition
H2O2 H2O + O2
Water decomposes with electricity Into its elements
Calcium carbonate decomposes to form calcium oxide and carbon dioxide
Hydrogen H+Tin Sn+2,Sn+4
Single replacement
Mg + HCl MgCl2 + H2
look up on activity series(p106)Mg must be higher than H for a
reaction
Mg + KCl No reactionMg is lower than K so “ no go”
Activity Series and History
What were some of the first metals used by man? Copper age @5 –4000 BC Why?
What age came next? Bronze age 3 – 2000 BC (Trojan war) What is bronze?
What age came next? Iron Age 1000 BC on
Why Bother Discussing This? Locate copper, tin and iron Copper is found in metallic form
It is an uncombined element Look below copper, gold, mercury and
silver “coinage” metals
Tin is easy to turn into its elemental form
Iron requires lots of energy!
LiKBaSrCaNaMgAlMnZnFeCdCoNiSnPbHCuAgHgAu
Ionic Compounds
When an ionic compound dissolves in water, what actually happens?
The battle between water and “columbic” attraction
•Particles of opposite charge are attracted to each other. •This attraction is called columbic attraction
Ionic Solution
So an ionic solution is really a bunch of charged particles floating around
Water “hydrates” or surrounds each particle
Water keeps the Plus and minus charges from attracting each other
If the plus and minus are more attracted to each other than to the water, then they combine and make a precipitate - it is not soluble
Double Replacement
Metal ions replace each other
All reactants are aqueous Check products on solubility
table to see if solid or aqueous
MgSO4 + NaCl BaSO4 + Ag2CO3
Combustion
Completehydrocarbon + O2 CO2 + H2O
C5H10 + O2 CO2 + H2O
IncompleteHydrocarbon + O2 CO + H2O
C + H2O
Practice
Balance and write the words:
Br2(l) + NaI(aq) NaBr(aq) + I2(s)
Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)
Practice
Balance and write the words:
Br2(l) + NaI(aq) NaBr(aq) + I2(s)
Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)
Practice
Balance and write the words:
Br2(l) + NaI(aq) NaBr(aq) + I2(s)
Al(s) +CuSO4 (aq)Al2(SO4)3(aq) +Cu(s)
C + O2 CO2
C-1 O-2 C- 1
O – 2