types of reactions 5 types of chemical reactions synthesis (combination) reaction decomposition...
TRANSCRIPT
Types of Reactions
5 Types of Chemical Reactions
Synthesis (Combination) reaction
Decomposition reaction
ASingle-replacement reaction
BDouble-replacement reaction
Combustion reaction (of a hydrocarbon)
A + B AB
AB A + B
A + BC AC + B
AB + CD AD + CB
CxHy + O2 CO2 + H2O + energy
Ause activity series to predictB use solubility chart to predict
Synthesis Reactions
General Formula: A + B AB
A is an elementB is an elementAB is a compound
Always write the correct formula for the compound based on the charges of the ions BEFORE balancing!
(identifying characteristic: only ONE product!)
Hints!! Don’t forget the formulas for diatomic elements, aka the “7-ups”
Synthesis ReactionExample: Sodium + chlorine
Na(s) + Cl2(g)
Na1+ Cl1-
1. Write the formulas for the reactant elements, including states of matter
2. Write the correct formula for the product compound based on the charge of the ions (remember that ionic compounds are solid at room temperature unless they are dissolved in water).
NaCl
Na(s) + Cl2(g) NaCl (s)
3. Balance the equation
22
Synthesis Reaction
Direct combination reaction (Synthesis)
General form: A + B AB
element element compound
Na+Cl -
Na
ClNa
Cl
Na+ Cl -
2 Na + Cl2 2 NaCl
Try this one!
Potassium + oxygen
The answer is…..
4 K(s) + O2 (g) 2 K2O (s)
K1+ O2-
K O
1 2
K2O
Write the ions
CrissCross the charges
Reduce if needed, ignore “1”
Decomposition Reactions
General formula: AB A + BIdentifying characteristic: only ONE reactant!
AB is a compoundA is an elementB is an element
Decomposition Reaction
Ex: decomposition of water
1. Write the formula of the reactant compound
H2O(l)
2. Write the formulas of the element products
H2(g) + O2(g)
3. Balance the equation
2 2
Decomposition Reaction
O O
O
HH
HH
H
H
H
HO
Decomposition reaction
2 H2O(l) 2 H2 (g) O2 (g)
General form: AB A B
+
+
+compound two or more elements
or compounds
Try this one!
The decomposition of iron(III) oxide(HINT: the roman numeral tells you the charge of the iron!)
2 Fe2O3(s) 4 Fe(s) + 3 O2(g)
Combustion Reactions
CxHy + O2 CO2 + H2O + energyA hydrocarbon*
•A hydrocarbon is a molecule that consists of carbonand hydrogen
Identifying characteristic:hydrocarbon and oxygen
Tips on Balancing Combustion Reactions
1. Do an Atom Inventory
2. 1st, balance the carbons
3. 2nd, balance the hydrogens
4. 3rd, balance the oxygens
5. If the oxygens don’t balance with a whole number, balance with a ½ number, THEN multiply all coefficients by 2.
Combustion of a Hydrocarbon
Many homes get heat from propane (C3H8) heaters. Write a balanced chemical equation for the completecombustion of propane gas.
C3H8(g) + O2(g) CO2(g) + H2O(g) + energy
C
H
O
3 18 2
2 3
1st Balance Carbons
3
/
/
3
7
2nd Balance hydrogens
/
4
8
3rd Balance oxygens
/ 10
5
/10
Do an Atom Inventory
Combustion of Methane Gas
Davis, Metcalfe, Williams, Castka, Modern Chemistry, 1999, page 245
One methane molecule
Two oxygen molecules
One carbondioxide molecule
Two water molecules
CH4 2 O2CO2 2H2O
1 carbon+
4 hydrogen4 oxygen
1 carbon+
2 oxygen
2 oxygen
+ 4 hydrogen
+ ++ energy
+
Heat and flame
Try this one!
Write the complete combustion equation for butane gas(formula for butane is C4H10). Butane is the gas found in lighters.
The answer is…….
2 C4H10 + 13 O2 8 CO2 + 10 H2O + energy
3. Balance O: C4H10 + O2 4 CO2 + 5 H2O + energy
1. Balance C: C4H10 + O2 CO2 + H2O + energy
2. Balance H: C4H10 + O2 4 CO2 + H2O + energy
4
5
(hint: need to use a ½)
6.5
4. Double all coefficients:
C4H10 + O2 CO2 + H2O + energy132 8 10
Single Replacement Reactions
General Formula: A + BC B + AC
Need to use an Activity Series to determine if a reaction will occur
Identifying characteristic: reactantsare an ELEMENT and a COMPOUND
A is an elementBC is a compoundA and B switch places to form: B (an element) and AC (a compound)
Single Replacement Reactions
Single-replacement reaction
Mg + CuSO4 MgSO4 + Cu
General form: A + BC AC + B
How do you know if Mg switches places with the Cu or the SO4?
If the element A forms a cation, it replaces the cation in the compound BC
If the element A forms an anion, it replaces the anion in the compound BC
Help, I need a review!!
What is a cation and an anion?
A cation is a “+” charged ion An anion is a “-” charged ion
Ionic Compounds are ALWAYSwritten cation then anion!!
Ex: MgCl2 Mg2+ Cl1-
Activity Series: Will a reaction occur ?
Element ReactivityLiRbKBaCaNaMgAlMnZnCrFeNiSnPbH2
CuHgAgPtAu
Halogen Reactivity
F2
Cl2Br2
I2
Al
Cu
Foiled again!Aluminum beats Copper!
Al (the element) is higher on the chart than Cu (in the compound)
Al is STRONGER so overtakes/replaces Cu in the compound andKicks Cu out by itself! Al
Cu
Al(s) + CuSO4 (aq)The cation list
The anion list
Aluminum vs copper II sulfate
Al (s) + CuSO4 (aq)
Al is higher on the chart than Cu, so it kicks Cu out of the compound.
Cu
Al then makes a compound with SO4
Al3+ SO42-3 2
Al (SO4)
+ Al2(SO4)3(aq)(s)
Now, balance the equation.
2 3 3
Your turn!
Will a reaction occur? Yes or No If “Yes”, write a complete balanced equation
NaNO3(aq) + Ag(s) ??
F2(g) + NaI(aq) ??
LiRbKBaCaNaMgAlMnZnCrFeNiSnPbH2
CuHgAgPtAu
F2
Cl2Br2
I2
Element Reactivity
Halogens
The Answers…
NaNO3(aq) + Ag(s) NR (abbrev for no reaction)
F2(g) + 2 NaI(aq) 2 NaF(aq) + I2(g)
Why? Because Ag (the element) is NOT higher on the chart than Na
Why? Because F2 IS higher on the chart than I2
Since F2 becomes the F- anion, it replaces the anion in NaI
Potassium reacts with Water
P O W !
*
2 HOH
* Often times it helps to think of water as HOH
Double Replacement Reactions
AB + CD CB + AD
Watch how the cations switch places!
A reaction ONLY occurs if at least ONE of the products is a solid (or H2O).A solubility chart is needed to determine if the products are solids or remain dissolved (aqueous).
Identifying characteristic:Both reactants are ionic compounds
1. Will Al(NO3)3
dissolve in water2. Will barium
phosphatedissolve in water?
3. Will PbI2 dissolve in water?
1. Yes2. No 3. No
Double Replacement ReactionsWill a reaction occur?
K2CO3(aq) + BaCl2(aq)
1. Determine the two products based on the charge of the ions
BaCO3 + KCl
2. Using the solubility chart, determine if each product is a. Aqueous (which means it is soluble in water)b. Solid (which means it is insoluble in water)
(s) (aq)
3. If one of the products is a solid, the reaction occurs, so BALANCE it
2
4. If BOTH products are aqueous, then NO REACTION occurs.Cross out products and write “NR”
Double Replacement Reaction
Double Replacement Practice
NaNO3(aq) + KCl (aq)
H2CO3(aq) + NH4(OH)(aq)
AgNO3(aq) + KCl(aq)
NaCl (aq) + KNO 3(aq)
(NH4)2CO3(aq) + 2 HOH(l)
NR
Formation of a solid AgCl
AgNO3(aq) + KCl(aq) KNO3 (aq) + AgCl(s)