Acids and bases

• acid (חומצה)

• base (בסיס)

• acid–base reaction

• Arrhenius definition:

  • acid: produces $\mathrm{H}{}^{+}$ in water
    • $\mathrm{HA}(\mathrm{aq})\to \mathrm{H}{}^{+}(\mathrm{aq})+\mathrm{A}{}^{-}(\mathrm{aq})$
  • base: produces $\mathrm{OH}{}^{-}$ in water
    • $\mathrm{BOH}(\mathrm{aq})\to \mathrm{B}{}^{+}(\mathrm{aq})+\mathrm{OH}{}^{-}(\mathrm{aq})$

• Brønsted–Lowry definition:

  • Brønsted–Lowry theory (aka: proton theory of acids and bases)
  • acid: proton ($\mathrm{H}{}^{+}$) donor
  • base: proton ($\mathrm{H}{}^{+}$) acceptor

• $\underset{\text{acid}}{\mathrm{HA}}+\underset{\text{base}}{\mathrm{B}}\rightleftharpoons \underset{\begin{array}{c}\text{conj.}\\ \text{base}\end{array}}{\mathrm{A}{}^{-}}+\underset{\begin{array}{c}\text{conj.}\\ \text{acid}\end{array}}{\mathrm{BH}{}^{+}}$

• conjugate acid

• conjugate base

• conjugate acid base pairs

• strong acid: completely deprotonated in solution

• strong base: completely protonated in solution

  • completely dissociates to produce $\mathrm{OH}{}^{-}$ in water

• weak acid: incompletely deprotonated in solution

  • $\mathrm{HA}\rightleftharpoons \mathrm{H}{}^{+}+\mathrm{A}{}^{-}$

• weak base: incompletely protonated in solution

  • $\mathrm{B}+\mathrm{H}{}_2\mathrm{O}\rightleftharpoons \mathrm{BH}{}^{+}+\mathrm{OH}{}^{-}$

• spectator ions (יונים משקיפים)

• acid strength

	acid/base dissociation constant
acid	$K_a=\frac{[\mathrm{H}{}^{+}][\mathrm{A}{}^{-}]}{[\mathrm{HA}]}$	$\underset{\mathrm{weak}\mathrm{acid}}{\mathrm{HA}(\mathrm{aq})}\rightleftharpoons \mathrm{H}{}^{+}(\mathrm{aq})+\underset{\text{conj. base}}{\mathrm{A}{}^{-}(\mathrm{aq})}$
	$K_a=\frac{[\mathrm{H}{}_3\mathrm{O}{}^{+}][\mathrm{A}{}^{-}]}{[\mathrm{HA}]}$	$\mathrm{HA}(\mathrm{aq})+\mathrm{H}{}_2\mathrm{O}(\mathrm{l})\rightleftharpoons \mathrm{H}{}_3\mathrm{O}{}^{+}(\mathrm{aq})+\mathrm{A}{}^{-}(\mathrm{aq})$
base	$K_b=\frac{[\mathrm{BH}{}^{+}][\mathrm{OH}{}^{-}]}{[\mathrm{B}]}$	$\mathrm{B}+\mathrm{H}{}_2\mathrm{O}\rightleftharpoons \mathrm{BH}{}^{+}+\mathrm{OH}{}^{-}$

• molecular autoionization (or self-ionization)

• protic solvent

• polyprotic acid

• self-ionization of water (יינון עצמי של מים)

  • $2\mathrm{H}{}_2\mathrm{O}\rightleftharpoons \mathrm{H}{}_3\mathrm{O}{}^{+}+\mathrm{OH}{}^{-}$
  • equilibrium constant: $K_{\mathrm{eq}}=\frac{[\mathrm{H}{}_3\mathrm{O}{}^{+}][\mathrm{OH}{}^{-}]}{[\mathrm{H}{}_2\mathrm{O}{]}^2}$
  • (ionic product of water) $K_{\mathrm{w}}=[\mathrm{H}{}_3\mathrm{O}{}^{+}][\mathrm{OH}{}^{-}]$ ($=1.0\times 10^{-14}$ at $25^{\circ }\mathrm{C}$)
    • $\mathrm{p}{K}_{\mathrm{w}}=-{\log }_{10}{K}_{\mathrm{w}}=\mathrm{pH}+\mathrm{pOH}$ ($=14$ at $25^{\circ }\mathrm{C}$)

• pH (ערך הֲגָבָה, רמת חומציות) of an aqueous solution (at a given temp.)

  • $\mathrm{pH}=-{\log }_{10}[\mathrm{H}{}_3\mathrm{O}{}^{+}]$
  • $\mathrm{pOH}=-{\log }_{10}[\mathrm{OH}{}^{-}]$
  • $\mathrm{p}{K}_a=-{\log }_{10}{K}_a$
  • $\mathrm{p}{K}_b=-{\log }_{10}{K}_b$
  • a solution with a $\mathrm{pH}=7$ at $25^{\circ }\mathrm{C}$ is neutral
  • Henderson-Hasselbalch equation
    • $\mathrm{pH}=\mathrm{p}{K}_a+{\log }_{10}\left(\frac{[\text{cont. base}]}{[\text{weak acid}]}\right)$

• neutralization (סתירה)

  • $\underset{\mathrm{strong}\mathrm{acid}}{\mathrm{HA}(\mathrm{aq})}+\underset{\mathrm{strong}\mathrm{base}}{\mathrm{BOH}(\mathrm{aq})}\to \underset{\mathrm{neutral}\mathrm{salt}}{\mathrm{BA}(\mathrm{aq})}+\mathrm{H}{}_2\mathrm{O}(\mathrm{l})$
    • net ionic equation: $\mathrm{H}{}^{+}(\mathrm{aq})+\mathrm{OH}{}^{-}(\mathrm{aq})\to \mathrm{H}{}_2\mathrm{O}(\mathrm{l})$
      • $\mathrm{H}{}_3\mathrm{O}{}^{+}(\mathrm{aq})+\mathrm{OH}{}^{-}(\mathrm{aq})\to 2\mathrm{H}{}_2\mathrm{O}(\mathrm{l})$
    • examples:
      • $\mathrm{HCl}+\mathrm{NaOH}\to \mathrm{NaCl}+\mathrm{H}{}_2\mathrm{O}$
      • $\mathrm{HNO}{}_3+\mathrm{KOH}\to \mathrm{KNO}{}_3+\mathrm{H}{}_2\mathrm{O}$

• Le Chatelier’s principle

• titration (or titrimetry or volumetric analysis) (טיטוּר, טיטרציה, תהליך סתירה)

  • standard solution (or titrant or titrator) (תמיסה תיקנית)

• buffer solution (בוּפר, מתריס, תמיסת מגן)

  • buffer capacity (קיבול הבופר)
  • acid buffer
    • examples:
      • $\mathrm{CH}{}_3\mathrm{COOH}/\mathrm{CH}{}_3\mathrm{CO}{}_2{}^{-}$
      • $\mathrm{HNO}{}_2/\mathrm{NO}{}_2{}^{-}$
      • $\mathrm{H}{}_2\mathrm{CO}{}_3/\mathrm{HCO}{}_3{}^{-}$
  • base buffer