Acids/ Basis

ions present at any given time in an equilibrium

=> e.g. H3O+: as soon as it forms, it reacts back to water, so only very small amounts of the ions are present at any given time

pH = - log cH3O+

=> neutral = pH = 7

• cH3O+ = 10^-7 = c OH-

2 H2O => H3O+ + OH-

=> Kw = ion-product constant for water

K+ = cH+ * cOH- = 10^-14

=> if concentration of one goes up, the other goes down

• substance that releases hydrogen ions, H+, in aqueous solution

• Acids cause an increase in H3O+ concentration

• hydrogen has no electron => called proton

• sour taste, corrosive (strong acids), color litmus paper red

H+ ions are much too reactive to exist alone => attach to water molecules to form H3O+

• produces hydroxide ions (OH-) in aqueous solutions

• Bitter taste, slippery feel when dissolved in water, turn red litmus paper blue

  
  

Strong = how much the acid/ base dissociates into ions in water on its own

• dissolve completely in water to release protons or hydroxide ions

E.g.

Strong acids: HCl (hydrochloride acid), HBr, HI, HF, HNO3 (nitric acid), H2SO4 (sulfuric acid), H2SO3 (sulphurous acid), H2PO4 (phosphoric acid)

Strong bases:

LiOH, NaOH, KOH, CsOH, RbOH, Ca(OH)2, Ba(OH)2

cause only a small amount of H3O+ or OH- increase in the aqueous solution

=> only dissociate to a small extent

weak bases react with water by taking an H+ and releasing OH- but only to a small extent

Base: NH3 / NH4OH; Mg(OH)2, Al(OH)3, CaCO3

Acid: CH3COOH/ CH3COO-

hydrogen ions and hydroxide ions form molecules of water

HCl + NaOH => NaCl + H2O

• other product is salt (ionic compound)

• occurs when there are enough moles of acid to react with all moles of base

• if there is an excess of moles of acid, the resulting solution will be acidic

• if there is an excess of moles of base, the resulting solution will be basic

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ions that appear unchanged on both side of the reaction

• important to consider when writing net ionic reactions from ionic ones

since pH is a log scale based on 10, a pH change of 1 unite represents a power of 10 change in H+

• solution with pH 2 has a cH+ ten times that of a solution with pH of 3

pH + pOH = 14

Acid rain: subsequent process from air pollution

Acid or Base spills: transport of chemicals or release of chemicals from industry

Ocean Acidification: Result of increasing amounts of CO2 in the atomsphere

• CO2 (weak acid) can react with H2O and form H2Co3.

• H2CO3 breaks apart into H+ and HCO3-

• H+ will react with shells (out of CaCO3) and forms HCO3-

• problems: H+ lowers the pH and CO32- is used from the shells and leads to a decrease of seashells and limestone

H+ reacts with carbonate ion in seawater to form bicarbonate (HCO3-) which reduces the concentration of carbonate ion in seawater. The calciumcarbonate in the shells of sea creatures begins to dissolve to maintain the concentration of carbonate ions in seawater:

CaCO3 => Ca2+ + CO32-

most responsible:

• SO2 and SO3 => combine with water to make H2SO4 (sulfuric acid) or H2SO3 (sulfurous acid)

• SO2 + H2O => H2SO3 => 2H+ + SO3 2-

• Nitrogen oxides (NO2 and NO3) that form HNO3 (nitric acid) with water

• 4 NO2 + 2 H2O + O2 => 4 HNO3 => H+ + NO3-

Acid rain

• reacts with metals

• reacts with limestones/ marble (CaCO3) to dissolve - such as statues and buildings)

• Acidification of lakes and streams: Acid can come from snow melts which contains SO42- anions. Effects fish, frogs, plankton, other species

• Forms aerosol haze above cities: Accelerated by sunlight, can cause/ aggravate respiratory illness

• burning of coal (1-3% of it is sulfur)

• S + O2 => SO2

• So2 in the air can react with oxygen:

• SO2 + 1/2 O2 => SO3

Nitrogen: NOx emissions are found in areas with heavy automobile traffic. Nitrogen dioxide gas in the atmosphere reacts with the hydroxyl radical to form nitric acid: NO2 + OH* => HNO3

• teck smelter spills

• chemical spills of salts, metals, and other materials into waterways can also result in change of pH in these aqueous environments

• plants need nitrogen in a chemical form that reacts more easily, such as the ammonium ion, ammonia, or the nitrate ion, in order to grow

• 1. Nitrogen fixation via bacteria: N2 => NH3 => NH4+ (w/H2O)

• 2. Nitrification (via bacteria): NH4+ => NO2- => NO3-

• 3. Denitrification (via bacteria): NO3- => NO => N2O => N2

  • energy is released

• Plants such as alfalfa, beans and peas remove N2 from the atmosphere, via bacteria living on or near the roots of the plants

Bacteria do not provide enough reactive nitrogen to supply the world with food, so synthetic fertilizers must be added:

N2 + H2 => 2NH3

• but needs very high temperatures and high pressure

• process uses 1-2% of total world energy production per year. This is more energy then generated by all the world solar panels per year (2016 1.3%)