chemical equation includes the substances being reacted (reactants), the substances being formed...
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Chemical Equation• Includes the substances being reacted (reactants), the
substances being formed (products), the phases of each of the substances, the number of moles of each substance, and the resultant energy change.
Reactants Products• Coefficients are placed in front of the substance
symbols to denote a mole ratio that is in accordance with the Law of Conservation of Mass.
HCl (aq) + Zn (s) H2 (g) + ZnCl2 (aq)
(reactants) (products)• This says that hydrochloric acid reacts with zinc metal
to form hydrogen gas and zinc chloride.
Word Equations
• A WORD EQUATION describes chemical change using the names of the reactants and products.
Write the word equation for the reaction of methane gas with oxygen gas to form carbon dioxide and water.
methane + oxygen
Reactant ProductCH4 O2 CO2 H2O
+ + 22
carbon dioxide + water
Checking for understandingWrite the word equation:Zn + HCl ZnCl2 + H2
Ca(OH)2 + H3PO4 Ca3(PO4)2 + H2O
6HCl + Fe2O3 2FeCl3 + 3H2O
The Law of Conservation of MassMass cannot be created or destroyed by physical or
chemical change. • The elements found in the reactants can be the only
elements found in the products, and there must be equal numbers of moles of those elements on both sides.
HCl (aq) + Zn (s) H2 (g) + ZnCl2 (aq)• Balancing equations involves placing coefficients that act
as multipliers in front of a substance's formula.2 HCl (aq) + Zn (s) H2 (g) + ZnCl2 (aq)
• This shows that 2 moles of HCl are required to react with 1 mole of Zn.
?
Visualizing a Chemical ReactionNa + Cl2 NaCl
___ mole Cl2 ___ mole NaCl___ mole Na
2
10 5 10
2
10 5 10
Tips for Balancing Equation
2 Cl vs Cl2
Cl2 means that there is one molecule of
diatomic chlorine.
2 Cl means that there are TWO
ATOMS of chlorine.
Diatomic molecules (Br2, I2, N2, Cl2, H2, O2, F2) exist whenever these elements are not in a compound with
another element.
Tips for Balancing Equation
• NEVER CHANGE THE CHEMICAL FORMULA!!! • You can ONLY write coefficients to balance!
3PO4
COEFFICIENT CHEMICAL FORMULA
Separation of NaCl
• In NaCl, there is one Cl-1 ion (since Na is charged +1), but if that chlorine is separated from that compound:
NaCl Na + Cl• Then the Cl’s thus formed will pair up
diatomically, which throws off the balancing:
NaCl Na + Cl2
Ex.1: carbon reacts with oxygen gas to produce carbon dioxide:
already balanced- 1: 1: 1Ex.2: hydrogen gas reacts with oxygen gas to produce water:
balanced ratio- 2: 1: 2
C + O2 CO2
C
O
1 1
2 2
H2 + O2 H2O
H
O
2 2
2 1
2
2x =4
2x =2
2
2x =4
Balance the following equations
• ZnS + O2 ZnO + SO2
2ZnS + 3O2 2ZnO + 2SO2
• Br2 + FeI3 I2 + FeBr3
3Br2 + 2FeI3 3I2 + 2FeBr3<Even and Odd rule>
Start off by putting an even number on the elements that are odd.
1. ___NaClO3 ___NaCl + ___O2
2. ___Fe3O4 + ___H2 ___Fe + ___H2O
Sample Problems:1. Hydrogen + oxygen water
3. Zinc + hydrochloric acid zinc chloride + hydrogen
3. Copper + silver nitrate cupric nitrate + silver
4. Ferric hydroxide iron (III) oxide + water
2 2 3
4 3 4
(Fe Single element)
H2 + O2 H2O22
Zn + HCl ZnCl2 + H22
Cu + AgNO3 Cu(NO3)2 + Ag2(Keep NO3 together)
2
Fe(OH)3 Fe2O3 + H2O2 3(O in multiple comp)
5. Ethane (C2H6) + oxygen carbon dioxide + water
6. Calcium + water calcium hydroxide + hydrogen
7. Potassium + sulfuric acid potassium sulfate + hydrogen
8. Calcium nitrate + aluminum sulfite calcium sulfite + aluminum nitrate
9. Phosphoric acid is formed when crystalline diphosphorus pentoxide is dissolved in water.
2Ca + H2O Ca(OH)2 + H2
K + H2SO4 K2SO4 + H22
C2H6 + O2 + H2OCO2 62 7 4
Ca(NO3)2 + Al2(SO3)3 CaSO3 + Al(NO3)33 3 2
P2O5 + H2O H3PO43 2
Combustion occur when a compound or element react with oxygen to
release energy and produce an oxideC3H8 + 5O2 3CO2 + 4H2O
+ +
General Form: CXHY + O2 CO2 + H2O
C C CHH
HH
H
H
HH
O OO OO OO OO O
CO O
CO O
CO O
OH H
OH H
OH H
OH H
+ ENERGY
Synthesis ReactionDirect combination reaction
Two elements combine to form a compound
General form: A + B AB
Na
ClNa
Cl
2 Na + Cl2 2 NaCl
ClNa
Na Cl
H
HH
H
Decomposition Reaction
H
HH
HO
Reverse of synthesisa compound decomposes into its original elements
2 H2O 2 H2 O2+
+
OO
O
General form: AB A + B
Be careful!
• DO NOT split the formula and rewrite.• MUST check the diatomic molecule!!!
2 H2O
H2 + O2
H2 + ODIATOMIC MOLECULE!!!!!!!!!!!WRONG!
CORRECT!
Single Replacement Reactionreplace one element from a compound with
another element
CuCl2 + Zn ZnCl2 Cu+
General form: A + BC B + AC where A is a metal, or
A + BC C + BA where A is a non-metal
ZnClCl Cu + ClCl
Zn Cu+
Be careful!
• DO NOT split the formula and rewrite.• MUST check the ion and charges!!!
Zn + HNO3
Zn(NO3)2 + H2
ZnNO3 + H
Charges are not balanced!WRONG!
CORRECT!
- 1+2 Diatomic Molecule
Single Replacement Reaction Practice
Al + Ag2CO3
1. Label the charges above each ion
2. Check the activity series 3. Write the product by
balancing the charges4. Balance the reaction
Al + Ag2CO3 Al2(CO3)3 + Ag2 3
+1 -2+3
ABOVE CAN REPLACE BELOW
Mg + AlCl3
Al + MgCl2
Predict if these reactions will occur
Al + MgCl2
Can magnesium replace aluminum?
Activity Series
YES, magnesium is more reactive than aluminum.
2 23 3
Can aluminum replace magnesium?
Activity Series
NO, aluminum is less reactive than magnesium.
Therefore, no reaction will occur.
No reaction
MgCl2 + Al No reaction
The question we must ask is can the single element replace its counterpart? metal replaces metal or nonmetal replaces nonmetal.
Order of reactants DOES NOT
determine how they react.
Double Displacement ReactionTwo solutions react to form a precipitate (solid) and another solution.
MgO + CaS MgS + CaO
General Form: AB + CD AD + CB
SOMg Ca
+O S
Mg Ca+
Be careful!
• DO NOT split the formula and rewrite.• MUST check the ion and charges!!!
K2CrO4 + 2AgNO3
KNO3 + Ag2CrO4
KNO3 + AgCrO4
Charges are not balanced!WRONG!
CORRECT!
+ 1 - 2
Precipitate• Insoluble ions remain together. • This is because the attractions
between the ions are too strong for water molecules to tear apart.
• The ions come together and form crystals, which make the solution cloudy.
• The crystals are pulled to the bottom of the solution by gravity, forming a PRECIPITATE.
K2CrO4 + 2AgNO3 Ag2CrO4 + 2KNO3
Solubility Rules
• Solubility rules can used to determine if a reaction will occur in a double displacement reaction.
• If both the products are soluble (form ions in solution), then no reaction has occurred.
Double Displacement Reaction3CoCl2(aq) + 2Na3PO4(aq) Co3(PO4)2(s) + 6NaCl(aq)
Will this reaction occur?
A reaction will occur only if the following
will be produced1)Gas
2)Solid precipitate
Solubility table
Precipitate
Verifying SolubilityUse your solubility chart to verity if the compound is soluble in water?
a) MgCO3
b) AgNO3
c) MgCl2
d) Na3PO4
e) KOH
InsolubleSolubleSolubleSolubleInsoluble
Double Replacement Reaction Practice
Na3PO4 (aq) + Mg(NO3)2 (aq)
1. Label the charges above each ion2. Write the product by balancing
the charges3. Check solubility using the rules4. Label the correct state5. Balance the reaction
+1 -3 +2 -1
Na3PO4 (aq) + Mg(NO3)2 (aq) NaNO3 + Mg3(PO4)2
INSOLUBLE
NaNO3 (aq) + Mg3(PO4)2(s)2 3 6
Oxidation vs. Reductiondriven by the loss of electrons (oxidation) and the
gain of electrons (reduction).
Oxidation-Reduction Reaction
• Oxidation is loss of electrons.
• Reduction is gain of electrons.
• There is a very easy way to do this. As long as you remember that you are talking about electron transfer:
Neutralizationoccur when an acid (most compounds starting with H) and a base
(most compounds ending in OH) react to form a salt and water.Acid + Base Salt + Water
+ +
General Form: HX + MOH MX + H2O
where X and M are elements
H Cl-Na+
O HH
OHCl-Na+
Checking for understandingExplain in exactly 10 words each process. Your sentences do have to make sense:OxidationReductionNeutralization
Stoichiometry Road Map
aA + bB cC + dD
Mass A
AtomsMolecules
A
Mol A Mol B
Mass B
AtomsMolecules
B
Mol Ratio
Molar mass
6.022 x 1023
Molar
mass
6.022 x 10 23
3 A + 4 B 2 D + 1 F
How many moles of F are produced from 1.00 mol of A?
1 mol A
3 mol A
1 mol F= 0.333 mol F
How many moles of D are produced from 5.00 mol of B?
5 mol B
4 mol B
2 mol D
= 2.50 mol D
How many moles of lithium carbonate are produced when 5.3 mol CO2 are reacted?
CO2(g) + 2LiOH(s) Li2CO3(s) + H2O(l)
1. What is your starting point?2. What is your ending point?
5.3 mol of CO2
mol of Li2CO3
5.3 mol CO2
1 mol CO2
1 mol Li2CO3
= 5.3 mol Li2CO3
3 A + 4 B 2 D + 1 FHow many grams of F are produced from 1.00 mol of A? If MM of F is 10.0g/mol.
1 mol A
3 mol A
1 mol F= 3.33g F
How many grams of D are produced from 5.00 mol of B? MM of D is 20.0g/mol
5 mol B
4 mol B
2 mol D
= 50.0g D
1 mol F
10 g F
1 mol D
20 g D
What is the mass of glucose (C6H12O6) produced from 3.00 mol of water (H2O)?
6CO2(g) + 6H2O(l) C6H12O6(s) + 6O2(g)
3 mol H2O
1. What is your starting point?2. What is your ending point?
3.00 mol of H2Og of C6H12O6
6 mol H2O
1 mol C6H12O6
1 mol C6H12O6
=90.1 g C6H12O6
180.81g C6H12O6
6CO2(g) + 6H2O(l) C6H12O6(s) + 6O2(g)
What is the mass of oxygen (O2) produced from 2.50 mol of water (H2O)?
1. What is your starting point?2. What is your ending point?
2.50 mol of H2Og of O2
2.5 mol H2O
6 mol H2O
6 mol O2
1 mol O2
32.0 g O2
=80.0 g O2
4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g)
How many moles of NO are formed from 824 g of NH3?
1. What is your starting point?2. What is your ending point?
824 g of NH3
mol of NO
824 g NH3
17.03g
1 mol NH3
4 mol NH3
4 mol NO
= 48.4 mol NO
3 A + 4 B 2 D + 1 FHow many grams of F are produced from 5.00g of A? If MM of F is 10.0g/mol and MM of A is 25.0g/mol
1 mole A
3 mole A
1 mole F= 0.677g F
How many grams of D are produced from 5.00g of B? MM of D is 20.0g/mol and MM of B is 10.0g/mol
1 mole B
4 mole B
2 mole D
=5.00g D
1 mole F
10 g F
1 mole D
20 g D
5 g A
25 g A
5 g B
10 g B
Sn(s) + 2HF(g) SnF2(s) + H2(g)
How many grams of SnF2 are produced from the reaction of 30.00 g HF?
1. What is your starting point?2. What is your ending point?
30.00 g of HFg SnF2
1 mol HF
2 mol HF
1 mol SnF2
= 117.5g SnF2
1 mol SnF2
156.71 g SnF2 30.00g HF
20.01g HF
Working a Stoichiometry Problem6.50 grams of aluminum reacts with an excess of oxygen. How many grams of aluminum oxide are formed?
1. Identify reactants and products and write the balanced equation.
Al + O2 Al2O3
b. What are the reactants?a. Every reaction needs a yield sign!
c. What are the products?
d. What are the balanced coefficients?
4 3 2