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