Topics 5 and 6 May 46 2020 As you go through the packet for this week you will see MANY familiar things Make sure to do ALL eight pages important What is familiar dissociation ID: 916451
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Slide1
Chemistry NotesAcids and BasesTopics 5 and 6 May 4-6, 2020
Slide2As you go through the packet for this week, you will see MANY familiar things. Make sure to do ALL eight pages- important!What is familiar?dissociation
vs dissolvingelectrolytes
dissociation equations
colligative properties
(BP elevation, and FP depression)
Slide3Remember- “Dissociation” is a special type of dissolving which is limited to ionic substances. If a material dissociates (splits) into ions, it is known as an electrolyte and will conduct electricity when dissolved in water
Slide4So, much of this week’s work is REVIEW, with a few additional topics. This is because we covered them during Unit 5 in January/FebruaryWhat is new? Ionization of molecules
strong vs weak acidsDilute vs concentrated solutions
Slide5What is IONIZATION of a molecular compoundsome molecular (covalent) compounds break apart into ions when they dissolve. This is called
ionization (NOT called dissociation, which is only for
ionics
)
Arrhenius acids are one example
of this. H
+
ions must be one
of
the ions
(that is the definition of Arrhenius acid)
Example :
HCl
(
aq
)
H
+
(
aq
)
+ Cl
-
(
aq
)
Most molecular (covalent)
compounds
will
not
ionize.
Slide6Slide7Equations- Dissociation vs ionizationIonic substances will dissociate in H2O (metal + nonmetal, polyatomic ion)
NaCl
(s)
–
H2O
-> Na
+
(
aq
)
+ Cl
-
(
aq
)
Most covalent substances will not ionize
Arrhenius acids will IONIZE
HF
(
aq
)
H
+
(
aq
)
+
F
-
(
aq
)
Slide8Strong vs Weak Acids Strong acids are strong electrolytes. This means that when they are dissolved in water, they completely ionize – every
single molecule of the strong acid will break apart into its ionsThe
strong acids are HI,
HBr
,
HCl
, HNO
3
, and
H
2
SO
4
(MUST KNOW FOR AP CHEMISTRY)
Slide9Strong vs Weak Acids Weak acids are weak electrolytes. This means that when they are dissolved in water, only some of the molecules stay ionized. The ionization of weak acids is a reversible reaction
An example of a weak acid is CH3
COOH
CH
3
COOH
CH
3
COO
-
(
aq
) + H
+
(
aq
)
Weak electrolytes contain fewer ions in solution and, therefore, a weaker electric current will pass through the solution
Slide10Dilutions Adding water to a solution will dilute it. The diluted Molarity will have a lower concentration.The new concentration
can be calculated using: M1
V
1
= M
2
V
2
M
1
and V
1
= molarity and concentration of original solution
M
2
and V
2
= molarity and concentration of diluted solution
Example: You need to prepare 250 mL of 0.10 M sodium hydroxide from a stock solution that is 2.0 M sodium hydroxide. How many mL of the stock solution must you dilute to achieve the desired solution?
Solution
: M
1
V
1
= M
2
V
2
(2.0 M)(V
1
) = (0.10 M)(250 mL)
V
1
; =
12.5 mL
Slide11Colligative properties (refresher)Boiling point elevation – boiling point of solvent increases when a solute is present Freezing point depression – freezing point of solvent decreases when a solute is presentThese properties depend on number of dissolved particles in solution (more particles dissolved in solvent = greater change in freezing and boiling point)