announcements
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Announcements. REMINDER: NO LAB THIS WEEK EXAM CLARIFICATION/FRIDAY DEADLINE SET CLICKER TO CHANNEL 41. Bases. Strong bases are hydroxide salts For now, only important weak base is NH 3 Ionization of weak acid produces a weak base. - PowerPoint PPT PresentationTRANSCRIPT
•REMINDER: NO LAB THIS WEEK
•EXAM CLARIFICATION/FRIDAY DEADLINE
•SET CLICKER TO CHANNEL 41
Announcements
Bases
Strong bases are hydroxide salts
For now, only important weak base is NH3
Ionization of weak acid produces a weak base
If the oxalate anion (C2O4-) reacts in an acid-base reaction,
which of the following can’t it make?
1 2 3
28%
53%
19%
1. H2C2O4
2. HC2O4-
3. 2CO2
Acid Base Reactions
Acid Base Reactions
Strong Acid + Strong Base
HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) acid base “salt” water
What do we get if we mix:
HBr (aq) + LiOH (aq)
Acid Base Reactions
Diprotic acids or bases
H2SO4(aq) + NaOH(aq)
H2SO4(aq) + Ba(OH)2(aq)
HCl(aq) + Ba(OH)2(aq)
Acid Base Reactions
Strong Acid + Weak Base
HCl(aq) + NH3(aq)
What do we get if we mix:
HNO3(aq) + NH3(aq)
Acid Base Reactions
Weak Acid + Strong Base (like strong acid+strong base)
HCN(aq) + NaOH(aq) NaCN(aq) + H2O(l) acid base “salt” water
What do we get if we mix:
HCOOH (aq) + KOH (aq) formic acid
Net Ionic Equations
1. Write a balanced chemical equation Molecular equation
1. Write out all the ions Total ionic equation
2. Cancel out anything that appears on both sides
Net ionic equation
Net Ionic Equations
HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)
What really happens:
H+(aq) + OH-(aq) H2O(l)
Sodium ion and chloride ion are “spectator ions”
Reactions Involving a Weak Base
Molecular equation:
HCl(aq) + NH3(aq) NH4Cl(aq)
Total ionic equation:
H+(aq) + Cl-(aq) + NH3(aq) NH4+
+ Cl-(aq)
Net ionic equation:
H+(aq) + NH3(aq) NH4+ (aq)
What is the net ionic equation for:
HNO3(aq) + NH3(aq) NH4NO3(aq)
CH3CO2H(aq) + NaOH(aq)
1 2 3
33% 33%33%1. CH3CO2H2
+(aq) + NaO(aq)
2. CH3CO2-(aq) + H2O(l) + Na+(aq)
3. CH4(g) + CO2(g) + H2O(l)
20
HCN(aq) + NH3(aq)
1 2 3
33% 33%33%
20
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
#
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++]]
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)