Chapter 6 (CIC) and Chapter 16 (CTCS) • Read in CTCS Chapter 16.1-3 • Problems in CTCS: 16.3, 5, 7, 9, 11, 15, 19, 21
Dec 30, 2015
Chapter 6 (CIC) and Chapter 16 (CTCS)
• Read in CTCS Chapter 16.1-3
• Problems in CTCS: 16.3, 5, 7, 9, 11, 15, 19, 21
Acid Rain• What’s an acid?
– Sour taste (vinegar, citrus)– Color changes with indicators– Reactions with carbonates (eggshells, seashells, marble)– According to Arrhenius: Release of H+ ions
Q: Concentrated hydrochloric acid is 37% by mass HCl. What is its’ molarity if its’ density is 1.19 g/mL?
HCl(g) H+(aq) + Cl-(aq)H2O
What’s a Base?• Opposite of acid• Bitter taste• Color changes with indicator• Slippery feel• According to Arrhenius: Release of OH- ions
Q: If the solubility of NaOH is 108 g/100. mL H2O, what is its’ molarity? Its’ density is 1.515 g/mL.
A: 19.7 M
NaOH(s) Na+(aq) + OH-(aq)H2O
Brønsted-Lowry• Arrhenius definition only good in water
• Brønsted-Lowry acid donates H+
• What is forming with NH3 and HCl?
• What is pH of NH3(aq)?
• NH3 accepts H+ (Brønsted-Lowry base)
HCl(g) H3O+(aq) + Cl-(aq)H2O(l)+
NH3(g) NH4+(aq) + OH-(aq)H2O(l)+
Amphoterism• Can’t have an acid without a base
• HCl + H2O • acid base
• NH3 + H2O • base acid
• Water is amphoteric – a substance that can behave as an acid or a base
Conjugate Acids/Bases
NH3(g) NH4+(aq) + OH-(aq)H2O(l)+
Base Acid Acid Base
• Conjugate acid/base pairs differ by H+
• The stronger an acid, the weaker its’ conjugate base
• What’s are strong, weak, and negligible acids?
Q: What are the conjugate bases of HC2H3O2, HNO3, H3O+?
Q: What are the conjugate acids of CO32-, HCO3
-, H2SO4?
Relative Strengths of Conjugate Acid/Base
Pairs
Q: Predict in which direction equilibrium lies:
HCl(aq) H2SO4(aq) + Cl-(aq)HSO4-(aq)+
HF(aq) H2SO4(aq) + F-(aq)HSO4-(aq)+
Neutralization• Acid + Base Salt + Water• HCl + NaOH NaCl + H2OQ: What is the net ionic equation for this?
• In order for complete neutralization, the concentrations of the acid and base must be the same
• [MH+] = [MOH-] • [MH+] > [MOH-] yields an acid• [MH+] < [MOH-] yields a base
• [MH+] x [MOH-] = 1 x 10-14
So, if one concentration is known, the other can be calculated
Q: If [MH+] = 1 x 10-7, then what is [MOH-]?
Autoionization of water
Did pure water conduct electricity?
H2O(l) H3O+(aq) + OH-(aq)H2O(l)+
Q: Calculate the concentration of [OH-] in a 0.001 M HCl solution
Q: Calculate the concentration of [H+] in a 1 x 10-15 M NaOH solution
Equilibrium
• If the forward rate = reverse rate then there is a constant amount of reactants and products
H2O(l) H3O+(aq) + OH-(aq)H2O(l)+
products
= reactants
K
+ - + -3 3
22 2 2
H O OH H O OH = =
H O H O H OcK
Q: What is [H2O]?
• This is also a constant, so
2 + -2 3H O = H O OHcK
+ - -143 = H O OH = 1 x 10wK