Transcript Complete ionic equation

Chemical Equation
• A representation of a chemical
reaction:
C2H5OH + 3O2  2CO2 + 3H2O
reactants
products
Chemical Equation
C2H5OH + 3O2  2CO2 + 3H2O
The equation is balanced.
1 mole of ethanol reacts with
3 moles of oxygen
to produce
2 moles of carbon dioxide and
3 moles of water
Molecular
representation of a rxn
Molecular rep of a rxn
Which of the following correctly describes the
balanced chemical equation given below? There may
be more than one true statement.
4Al + 3O2  2Al2O3
I.
For every 4 atoms of aluminum that react with
6 atoms
of oxygen, 2 molecules of aluminum
oxide are produced.
II.
For every 4 moles of aluminum that react with
3 moles
of oxygen, 2 moles of aluminum oxide are
produced.
III. For every 4 grams of aluminum that react with
3 grams
of oxygen, 2 grams of aluminum oxide
are produced.
Rules for Balancing Reactions
• For each element, the number of atoms on
the reactant side must equal the number of
atoms on the product side.
• The subscripts cannot change. Only
coefficients can be changed.
• The coefficients must be whole numbers.
• The coefficients must be simplified (divided
down) as much as possible.
Which of the following correctly balance the
chemical equation given below? There may
be more than one correct balanced equation.
CaO + C  CaC2 + CO2
I.
II.
III.
IV.
CaO2 + 3C  CaC2 + CO2
2CaO + 5C  2CaC2 + CO2
CaO + (2.5)C  CaC2 + (0.5)CO2
4CaO + 10C  4CaC2 + 2CO2
Which of the following statements are true
concerning balanced chemical equations?
There may be more than one true statement.
I.
The number of molecules is conserved.
II. The coefficients tell you how much of each
substance you have.
III. Atoms are neither created nor destroyed.
IV. The coefficients indicate the mass ratios of
the substances used.
V.
The sum of the coefficients on the
reactant side equals the sum of the
coefficients on the product side.
1.
CH4
+
2. SiO2 +
3. K
+
4. C2H6
+
5. NH3 +
O2

CO2
+
H2O
HF

SiF4
+
H2O
H2O

H2
+
KOH
O2

CO2
+
H2O
O2

NO
+
H2O
1.
H2SO4
2.
Fe(CN)3 +
3.
K3PO4
+
+
Ca(OH)2
MgCl2 
H2O


CaSO4
FeCl3
H3PO4
+
H2O
+ Mg(CN)2
+
KOH
Reaction Symbols
• (s) solid
• (l) liquid
• (g) gas
• (aq) aqueous = dissolved in water
• △ heat added (put over arrow)
Diatomic Molecules
• Remember which atoms make
diatomic molecules:
– H2 and N2, O2, F2
Cl2
Br2
I2
-This is only when they are by
themselves!
-When other atoms are by themselves
they don’t have any subscripts, for
example iron is just Fe
Write the balance chemical equation for
the following:
1) Hydrogen gas is ignited and burns,
combining with oxygen to form water
vapor.
2) Silver oxide is decomposed by strong
heating into silver metal and oxygen
gas.
3) Methanol (CH3OH) is synthesized from
carbon monoxide gas and hydrogen
gas.
4) If iron (III) oxide is heated strongly in
a stream of carbon monoxide gas, it
produces elemental iron and carbon
dioxide gas.
Classifying Reactions
8 different types of reactions:
1.
Precipitation reactions
(aq) + (aq)  (s) + (aq) or (l)
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
2. Acid-base reactions
--OH + H--  salt + H2O(l)
NaOH(aq) + HCl(aq)  NaCl(aq) + H2O(l)
3. Oxidation-reduction reactions
uncombined element on one side is combined
on the other side
Fe2O3(s) + Al(s)  Fe(l) + Al2O3(s)
4. Synthesis – one product
N2 + O2  2NO
5. Decomposition – one reactant
2H2O  2H2 + O2
6. Combustion – O2 is a reactant, O adds
to each element
If C and H, then CO2 + H2O are the
products
CH4 + 2O2  CO2 + 2H2O
Another way to classify:
7. Double displacement – “doubles” on both
sides
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
8. Single displacement – a “single” and a
“double” on both sides
Fe2O3(s) + Al(s)  Fe(l) + Al2O3(s)
Precipitation Reactions
• Form a solid (s) on product side
• Must have only (aq) on reactant side
• The solid formed is NOT a strong
electrolyte
Pb(NO3)2(aq) + 2NaI(aq)  PbI2(s) + 2NaNO3(aq)
• Is the product a solid?????
– Will NOT be solid if:
•It contains a group I metal
•It contains NH4+
•It contains NO3-
Complete and balance the precipitation
reactions:
a) LiOH(aq) + MgS(aq) 
b) PbCl2(aq) + KBr(aq) 
Identify the precipitate (solid) in each
case!
Acid-Base Reactions
• Also called neutralization reactions
• Acids: they have H’s at the front,
e.g. H2SO4
– Their function is to give their H’s away
• Bases: they have OH’s at the end,
e.g. Ba(OH)2
– Their function is to take the acids H’s
and combine with their OH’s to make
H2O
• Strong bases are always aq, never solid:
– Group I with OH
•LiOH
•NaOH
•KOH
•RbOH
•CsOH
- Certain Group II with OH
- Ca(OH)2
- Sr(OH)2
- Ba(OH)2
Equations that show the dissociation:
Strong acids -dissociate completely in water to
produce H+ ions.
HCl  H+ + ClH2SO4  2H+ + SO42Strong bases - dissociate completely in water
to produce OH ions.
NaOH  Na+ + OHBa(OH)2  Ba2+ + 2OH-
Acid-Base Reactions
• Always produce water and salt
Salt = metal from base and leftovers
from acid
HNO3(aq) + KOH(aq) 
H2SO4(aq) + LiOH(aq) 
H3PO4(aq) + Ca(OH)2(aq) 
QUESTION
In the balanced equation for the neutralization of
sodium hydroxide with sulfuric acid, the products are:
a)
b)
c)
d)
e)
NaSO4 + H2O
NaSO3 + 2H2O
2NaSO4 + H2O
Na2S + 2H2O
Na2SO4 + 2H2O
ANSWER
e)
Na2SO4 + 2H2O
Give the acid base reaction that will
produce the following salts:
a) K2SO4
b) CsNO3
• Sr(OH)2 + H3PO4 
Redox Reactions
• Oxidation-reduction (redox)
– The oxidation number (charge) changes
from reactant side to product side
– Is a transfer of electrons
– Element is alone on one side, but
combined with other element(s) on the
other side
2Mg + O2  2MgO
H2O(l)  H2(g) + O2(g)
QUESTION
Give the reaction type for each of the following
reactions:
Pb(NO3)2(aq) + 2NaI(aq)  PbI2(s) +2Na(NO3)(aq)
Na(s) + LiCl(aq)  Li(s) + NaCl(aq)
HClO3(aq) + KOH(aq)  KClO3(aq) + H2O(l)
ANSWER
precipitation,
redox,
acid-base
3 more Reaction Types
• Synthesis – one product
N2 + O2  2NO
• Decomposition – one reactant
2H2O  2H2 + O2
• Combustion – O2 is a reactant,
CO2 + H2O are the products
CH4 + 2O2  CO2 + 2H2O
Another way to classify:
– Double displacement
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
– Single displacement
Fe2O3(s) + Al(s)  Fe(l) + Al2O3(s)
1.
CH4
+
2. SiO2 +
O2

CO2
+
H2O
HF

SiF4
+
H2O

H2
3. K
+
H2O
4. Fe
+
O2
5. NH3 +
O2
+
KOH
Fe2O3


NO
+
H2O
1.
H2SO4
2.
Fe(CN)3 +
3.
K3PO4
+
+
4. CaCO3 
Ca(OH)2

MgCl2 
H2O

CaO + CO2
CaSO4
FeCl3
H3PO4
+
H2O
+ Mg(CN)2
+
KOH
Electrolytes
Strong – break up into + and – in
water
NaCl  Na+ + ClWeak – only a few molecules
break up in water
vinegar solution
Non - no molecules break up in
water
sugar solution
Strong Electrolytes
• Compounds containing a group 1 metal
• Compounds containing NH4+
• Compounds containing NO3• Strong acids
• Strong bases
The 7 Strong Acids
• HCl
• HBr
• HI
• HNO3
• H2SO4
• HClO4
• HClO3
The 8 Strong Bases
• LiOH
• NaOH
• KOH
• RbOH
• CsOH
• Ba(OH)2
• Sr(OH)2
• Ca(OH)2
Describing Reactions in Solution
1. Molecular equation
(reactants and products as compounds)
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
2. Complete ionic equation
(all strong electrolytes shown as ions)
Ag+ + NO3 + Na+ + Cl  AgCl(s) + Na+ + NO3
Describing Reactions in
Solution (continued)
3.
Net ionic equation (show only
components that actually react)
Ag+ + Cl  AgCl(s)
Na+ and NO3 are spectator ions.
Write the balanced net ionic equation for the
following reaction:
Pb(NO3)2(aq) + H2SO4(aq)  PbSO4(s) + HNO3(aq)
Give the molecular equation for
Ni(NO3)2 + NaOH 
Give the net ionic equation for
Ni(NO3)2 + NaOH 
Give the complete ionic equation for
Ni(NO3)2 + NaOH 
What were the spectator ions in that
equation?