Unit 4: Acids & Bases

Note: This page is currently under development, there are no guarantees that answers are correct

PH Conversions

PH pOH [H+] [OH-] Acid / Base / Neutral
-
How to
  1. Calculate PH
    • PH from pOH: 14 - pOH = PH
    • PH from H: -log10(H); = PH
    • PH from OH: -log10(14 - OH) = PH
  2. Plug PH In
    • pOH from PH: 14 - PH = pOH
    • [H+] from PH: 10-PH = [H+]
    • [OH-] from PH: 10-(14 - PH) = [OH-]
Note Sig Figs

pH and pOH have one 1 more decimal place than [H+] and [OH-]

Conjugate Bases and Acids

Bases ⇄ Acids

Bases Acids
Rule Bases give away one H, and in most cases, subtract 1 from the charge Acids take one H, and in most cases, add 1 to the charge
Example
  • HOCl -> OCl-
  • HNO2 -> NO2-
  • H2SO3 -> HSO3-
  • HC2O4- -> C2O42-
  • NH3 -> NH4+
  • C6H5NH2 -> C6H5NH3+
  • HSO3- -> H2SO3
  • C2O42--> HC2O4-

Ka and Kb expressions

Acid / Base Water → Element #1 Element #2 Acid or Base
H2O (I) →
Example
HCN (aq) H2O (I) → H3O+ (aq) CN- (aq)
How to determine if an element is an acid or base
  1. Count the hydrogens on the substance that is before and after the reaction.
  2. If the number of hydrogens has decreased that substance is the acid. If the number of hydrogens has increased that substance is the base.

Kb = [Output Element #1][Output Element #2]/[Original Element]

Titrations

Solve for volume needed to titrate

Element #1 Element #2
Molarity (M) Volume Molarity (M) Volume
-

M1V1= M2V2 → * = * x → * / = ___
- Remember to add measurements and the element

Solve for molar mass of Titrated element

Weight of Element #1 (g) Volume of Element #2 (ml) Molarity of Element #2 (M)
  1. Moles of #1 = * (1L / 1000 ml) * = __ mols
  2. Moles of 2 = Moles of #2 = __
  3. Molar Mass of #2 = / __ = NaN g/mol

Titration Tables

Strong Base/Strong Acid

Molarity of Acid Volume of Acid (ml) Molarity of Base Volume of Base (ml)
  1. M [H] * ml = mol [H]
  2. M [OH-] * ml = mol [OH-]
  3. As we have fewer mols of the base, it is limiting, and we will subtract it from the acid
    - = mols
  4. New Volume = ml + ml = ml
  5. Molarity = / = M
  6. pH = -log() =
  7. pOH = 14 - pH = 14 - =

Strong Acid/Weak Base

Molarity of Acid (M) Volume of Acid (ml) Molarity of Base (M) Volume of Base (ml) Kb

Weak Acid/Strong Base

Molarity of Acid (M) Volume of Acid (ml) Molarity of Base (M) Volume of Base (ml) Ka
Acid Formula Conjugate Base Ka pKa
iodic acid HIO3 - 0.17 0.77
oxalic acid H2C2O4 - 5.9*10‒2 1.23
sulphurous acid H2SO3 - 1.5*10‒2 1.82
hydrogen sulphate acid HSO4‒ - 1.2*10‒2 1.92
chlorous acid HClO2 - 1.2*10‒2 1.92
phosphoric acid H3PO4 - 7.5*10‒3 2.12
hydrofluoric acid HF - 7.2*10‒4 3.14
nitrous acid HNO2 - 4.0*10‒4 3.4
hydrogen oxalate acid HC2O4‒ - 6.1*10‒5 4.21
acetic acid HC2H3O2 (or CH3COOH) - 1.8*10‒5 4.74
carbonic acid H2CO3 - 4.3*10‒7 6.37
hydrogen sulphite acid HSO3‒ - 1.0*10‒7 7
hydrosulphuric acid H2S - 1.0*10‒7 7
dihydrogen phosphate acid H2PO4‒ - 6.2*10‒8 7.21
hypochlorous acid HOCl - 3.5*10‒8 7.46
hypobromous acid HOBr - 2.0*10‒9 8.7
hydrocyanic acid HCN - 6.2*10‒10 9.21
boric acid H3BO3 - 5.8*10‒10 9.24
ammonium acid NH4+ - 5.6*10‒10 9.25
hydrogen carbonate acid HCO3‒ - 5.6*10‒11 10.25
hydrogen phosphate acid HPO42‒ - 4.8*10‒13 12.32
hydrogen sulphide acid HS‒ - 1.3*10‒13 12.89
Base Formula Conjugate Acid kb pkb
diethylamine C4H10NH C4H10NH2+ 1.3x10‒3 2.89
ethylamine C2H5NH2 C2H5NH3+ 5.6x10‒4 3.25
methylamine CH3NH2 CH3NH3+ 4.4x10‒4 3.36
triethylamine C6H15N C6H15NH+ 4.0x10‒4 3.4
ammonia NH3 NH4+ 1.8x10‒5 4.74
hydrazine H2NNH2 (or N2H4) H2NNH3+ (or N2H5+) 3.0x10‒6 5.52
hydroxylamine HONH2 (or ONH3) HONH3+ (or ONH4+) 1.1x10‒8 7.96
pyridine C5H5N C5H5NH+ 1.7x10‒9 8.77
aniline C6H5NH2 C6H5NH3+ 3.8x10‒10 9.42