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•OWL HOMEWORK
Announcements
CH3CO2H(aq) + NaOH(aq)
1 2 3
11% 12%
77%1. CH3CO2H2
+(aq) + NaO(aq)
2. CH3CO2-(aq) + H2O(l) + Na+(aq)
3. CH4(g) + CO2(g) + H2O(l)
HCN(aq) + NH3(aq)
1 2 3
88%
5%7%
1. NH4+(aq) + CN-(aq)
2. H2CN+(aq) + NH2-(aq)
3. C2N2(s) + 3 H2(g)
The pH Scale
Quantitative measure of solution acidity
Remember solution concentration:
[NaCl]=0.25M means 0.25 moles of NaCl are in 1L of solution
solventL
solutemolesMolarity
1
#
How much of a 1.oM HCl solution should I add to neutralize 1.0L of 0.1M NaOH?
1.0L0.1M NaOH
1 2 3 4 5
5%
21%
8%
24%
42%1. 1.0 mL2. 10.0 mL3. 100.0 mL4. 1.0 L5. 10.0 L
The pH Scale
In pure water, some molecules ionize to form H3O+ and OH-
H2O + H2O OH– + H3O+
In acidic and basic solutions, these concentrations are not equal
acidic: [H3O+] > [OH–]
basic: [OH–] > [H3O+]
neutral: [H3O+] = [OH–]
The pH Scale
pH scale= measure of [H3O+]pH < 7.0 = acidicpH > 7.0 = basicpH = 7.0 = neutral
Measure of H3O+ concentration (moles per liter) in a solution
As acidity increases, pH decreases
The pH Scale
The pH scale is logarithmic100100 101022 log(10log(1022) = 2) = 21010 101011 log(10log(1011) = 1) = 111 101000 log(10log(1000) = 0) = 00.10.1 1010–1–1 log(10log(10–1–1) = –1) = –10.010.01 1010–2–2 log(10log(10–2–2) = –2) = –2
pH = –log [HpH = –log [H33OO++]]
Logs- a quick review
log N = a 10a = N
Example
log 4 = 0.602 100.602 = 4
The pH Scale
pH = –log [HpH = –log [H33OO++]]
pH if [HpH if [H33OO++] = 10] = 10–5–5? 10? 10–9–9??
Acidic or basic?Acidic or basic?
pH if [HpH if [H33OO++] = 0.000057 M?] = 0.000057 M?
Finding [H3O+] from pH
[H[H33OO++] = 10] = 10-pH-pH or [H or [H33OO++] = log] = log-1-1 (-pH) (-pH)
Finding the inverse log (or log Finding the inverse log (or log -1-1)of a number )of a number on your calculator:on your calculator:
Enter the number, press the inverse (inv) or shift button, Enter the number, press the inverse (inv) or shift button, the press the log button (it might be labeled 10the press the log button (it might be labeled 10xx))
What is [HWhat is [H33OO++] if pH = 8.6?] if pH = 8.6?
pH: Quantitative Measure of Acidity
Acidity is related to concentration of H+ (or H3O+)
pH = -log[H3O+]
[H3O+]= 10-pH = log-1(-pH)
pOH measures basicity
pOH=-log[OH-]
pH + pOH = 14
Precipitation Reactions
Solubility of Ionic Compounds
dissolving
How to determine if an ionic compound is soluble
Identify the two ions
Check the “solubility rules” Soluble ions with no “exceptions” never form
precipitates
If one of the ions is insoluble, the compound is insoluble
Make sure to check for “exceptions”
Example: K2CO3
If a reaction product is insoluble, it will form a precipitate
Examples
Soluble or Insoluble?
1. NaNO3
2. FeCl3
3. Fe(OH)3
4. BaSO4
5. AgNO3
6. AgCl
More Examples (on your handout- try at home)
Soluble or Insoluble?
7. K3PO4
8. Fe3(PO4)2
9. PbCl2
10. FeSO4
11. (NH4)2S12. PbS
When potassium chromate and barium nitrate react, which product precipitates?
1 2 3
57%
17%
26%
1. BaCrO4
2. KNO3
3. Both products are insoluble
Precipitation ReactionsNet Ionic Equations
Pb(NO3)2 + K2CrO4 ?
Pb(NO3)2 + KI ?
BaCl2 + KNO3
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