Vocabulary

1
Vocabulary

• In SOLUTION we need to define the -
• SOLVENT the component whose physical state is
  preserved when solution forms
• SOLUTE the other solution component
• The CONCENTRATION is most often expressed by
  chemists as MOLARITY. Other common expressions of
  concentration are w/w, vol/vol, and normality.

2
1.0 L of water was used to make 1.0 L of
solution. Notice the water left over.
CCR, page 206
3
PROBLEM Dissolve 5.00 g of NiCl26 H2O in
enough water to make 250 mL of solution.
Calculate molarity of the solution and the
concentration of each of the ions.
4

• Problem What mass of oxalic acid, H2C2O4, is
  required to make 250. mL of a 0.0500 M solution?

5
PROBLEM You have 50.0 mL of 3.0 M NaOH and you
want 0.50 M NaOH. What do you do?
6
SOLUTION STOICHIOMETRYSection 5.10

• Zinc reacts with acids to produce H2 gas.
• Have 10.0 g of Zn
• What volume of 2.50 M HCl is needed to convert
  the Zn completely?

7
Zinc reacts with acids to produce H2 gas. If you
have 10.0 g of Zn, what volume of 2.50 M HCl is
needed to convert the Zn completely?
8
Aqueous Solutions

• Non-Electrolytes they dissolve, but wont
  conduct electricity. These are generally polar
  solids capable of forming hydrogen bonds
• Sugar, ethanol, ethylene glycol
• Strong Electrolytes Completely dissociates,
  conducts electricity well most ionic solids and
  strong acids
• Weak Electrolytes Dissolve, ionize to a small
  extent, conducts electricity weakly. Weak acids,
  such as Acetic acid, ionize only to a small
  extent, so it are a weak electrolyte.
• CH3CO2H(aq) ? CH3CO2-(aq) H(aq)

9
Water Solubility of Ionic Compounds
If one ion from the Soluble Compound list is
present in a compound, the compound is water
soluble.
10
There are three ways to write reactions in
aqueous solutions. Molecular equation Show all
reactants products in molecular or ionic form
Total ionic equation Show the ions and
molecules as they exist in solution
Net ionic equation Shows ions that participate
in reaction and removes spectator ions. Spectator
ions do not participate in the reaction.
11
Net Ionic Equations

• Mg(s) 2HCl(aq)? H2(g) MgCl2(aq)
• The molecular formula above can be written as the
  total ionic formula
• Mg(s) 2H(aq) 2Cl-(aq)? H2(g) Mg2(aq)
  2Cl-(aq)
• The two Cl- ions are SPECTATOR IONS they do not
  participate. Could have used NO3- for the
  spectator ion as salts of nitrates are all
  soluble.
• By leaving out the spectator ions out you get the
  net ionic reaction
• Mg(s) 2 H(aq) ---gt H2(g) Mg2(aq)

12
ACIDS Table 5.2
A Brönsted-Lowry Acid ? H in water

• Strong Brönsted-Lowry acids are strong
  electrolytes
• HCl hydrochloric
• H2SO4 sulfuric
• HClO4 perchloric
• HNO3 nitric

Weak Brönsted-Lowry acids are weak
electrolytes CH3CO2H acetic acid (CH3COOH)
H2CO3 carbonic acid H3PO4 phosphoric acid HF
hydrofluoric acid
Carbonic Acid
13
Ammonia, NH3 an Important weak Base
BASES Table 5.2
Brönsted-Lowry Base ? OH- in water

• NaOH(aq) ? Na(aq) OH-(aq)

NaOH is a strong base
14
ACIDS

• Nonmetal oxides can be acids
• CO2(aq) H2O(l) ? H2CO3(aq)
• SO3(aq) H2O(l) ? H2SO4(aq)
• NO2(aq) H2O(l) ? HNO3(aq)
• Acid Rain is an example of nonmetal oxides
  behaving as acids. This process can result from
  burning coal and oil.

BASES

• Metal oxides can be bases
• CaO(s)H2O(l) ? Ca(OH)2(aq)

CaO in water. Phenolphthalein indicator shows a
of calcium oxide solution is basic.
15
You should know the strong acids bases
16
A brief history of Acid-Base Identification
Systems
System Acid (HCl) Base (NaOH)
Arrhenius
Brönsted-Lowry
Lewis
17
pH, a Concentration Scale

• pH a way to express acidity -- the concentration
  of H in solution.

Low pH high H
High pH low H
Acidic solution pH lt 7 Neutral pH 7 Basic
solution pH gt 7
18
The pH Scale

• pH log (1/ H) - log H
• In a neutral solution, H OH- 1.00
  x 10-7 M at 25 oC
• pH - log H
• If the H of soda is 1.6 x 10-3 M, the pH is
  ____.
• If the pH of Coke is 3.12, it is _____.

19
ACID-BASE REACTIONSTitrations

• H2C2O4(aq) 2 NaOH(aq) ? Na2C2O4(aq) 2 H2O(l)
• acid base
• Carry out this reaction using a TITRATION.

20
Titration

• 1. Add solution from the buret.
• 2. Reagent (base) reacts with compound (acid) in
  solution in the flask.
• 3. Indicator shows when exact stoichiometric
  reaction has occurred.
• 4. Net ionic equation
• H OH- --gt H2O
• 5. At equivalence point
• moles H moles OH-

21
PROBLEM Standardize a solution of NaOH i.e.,
accurately determine its concentration. 1.065 g
of H2C2O4 (oxalic acid) requires 35.62 mL of NaOH
for titration to an equivalence point. What is
the concentration of the NaOH?
22
PROBLEM Use standardized NaOH to determine the
amount of an acid in an unknown. Apples contain
malic acid, C4H6O5. 76.80 g of apple requires
34.56 mL of 0.663 M NaOH for titration. What is
weight of malic acid?
C4H6O5(aq) 2NaOH(aq) ? Na2C4H4O5(aq) 2
H2O(l)
23

• Types of Reactions
• Combination Reactions
• More than one reactant, one product
• Decomposition Reactions
• Single reactant, more than one product
• Displacement Reactions
• One element displaces another from a compound
• Redox Oxidation Reduction Reactions
• Oxidation numbers of some elements change at
  least one element must increase and one must
  decrease in oxidation number.
• Metathesis Reactions - Exchange Reactions
• Precipitation products include an insoluble
  substance which precipitates from solution as a
  solid
• Acid-base neutralization product is a salt and
  water
• Gas formation primarily the reaction of metal
  carbonates

24
OXIDATION NUMBERS

• NH3
• ClO-
• H3PO4
• MnO4-
• Cr2O72-

25
Recognizing a Redox Reaction

• 2 Al(s) 3 Cu2(aq) ? 2 Al3(aq) 3 Cu(s)

26
Oxidation-Reduction Reactions

• Thermite reaction
• Fe2O3(s) 2Al(s) ? 2 Fe(s) Al2O3(s)

2Al(s) 3Cu2(aq) ? 2Al3(aq) 3Cu(s)
2 H2(g) O2(g) ? 2H2O(l)
In all reactions if something has been oxidized
then something has also been reduced.
Redox reactions are characterized by ELECTRON
TRANSFER between an electron donor and electron
acceptor. Transfer leads to 1. increase in
oxidation number of some element
OXIDATION 2.decrease in oxidation number of some
element REDUCTION
27
Chemical Reactions in WaterMetathesis

• EXCHANGE REACTIONS

The anions exchange places between cations.
Precipitation Pb(NO3)2(aq) 2 KI(aq) ? PbI2(s)
2KNO3(aq) Pb2(aq) 2 I-(aq) ?
PbI2(s) Neutralization NaOH(aq) HCl(aq)?
NaCl(aq) H2O(l) OH-(aq) H(aq) ?
H2O(lq) Gas Formation MgCO3(s) 2HCl(aq) ?
2Mg(Cl)2(aq) H2O(l) CO2(g)
28
(No Transcript)