8. Acids and Bases

Proton donor (H2)

Proton acceptor (NH3)

electron pair acceptor (H+ in H2O acts as the electrophile)

electron pair donor (water acts as the nucleophile)

can act as either an acid or a base eg Al2O3

A type of amphoteric substance that specifically can act as either an acid or base by accepting / donating H+ ions

pH = -log10[H+] [H+] = 10-pH

Kw = [H+][OH] = 1 x 10-14 mol2dm-6 pKw = 14 = pH +pOH

pH decreases as the temp increases

• Hydrochloric acid • Nitric acid • Sulfuric acid

• Carboxylic acids (eg ethanoic acid) • Carbonic acid

• Group 1 hydroxides (eg NaOH) • Barium hydroxide

• Ammonia • Amines

CO2(g) + H2O(l) <—> H2CO3(aq) H2CO3(aq) <—> H+(aq) + HCO3-(aq) HCO3-(aq)​ <—> H+(aq) + CO32-(aq) precipitation below pH 5.6 is considered acid deposition

at high temps such as in engines N2(g) + O2(g) –> 2NO(g) this reacts further with oxygen 2NO(g) + O2(g) –> 2NO<strong>2(g)</strong> this then reacts with water 2NO2(g) + H2O(l) –> HNO3(aq) + HNO2(aq)

sulphur diozide is released by burning coal S(s) + O2(g) –> SO(g) this reacts with water to form sulfurous acid SO2(g) + H2O(l) <—> H2SO3(aq) this can also react further with air, then water to form sulphuric acid 2SO2(g) + O2(g) <—> 2SO3(g) SO3(g) + H2O(l) –> H2SO4(aq)

Pre-combustion methods • involve crushing and cleaning coal to remove up to 90% of solid sulphur Post-combustion methods • calcium oxide or lime can remove gaseous sulphur (and other pollutants)

[H+] = sqrt Ka[HA] pKw = pH + pOH = 14 Kw = KaKb = 10-14

weak acid + its sodium/ potassium salt eg ethanoic acid sodium ethanoate

Weak base + its chloride eg ammonia ammonium chloride