Chemistry in water
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Chemistry in Water. Chem Rxns in Aqueous Solns Solvent = Water Solute = acid, base or salt. IONIC COMPOUNDS. Salt: constituent ions form solid crystal lattice, high MP, dissolves in H 2 O to give cations (+) and anions (-) surrounded by polar H 2 O molecules (Fig 11.1)

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Chemistry in Water

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Chemistry in water

Chemistry in Water

Chem Rxns in Aqueous Solns

Solvent = Water

Solute = acid, base or salt


Ionic compounds

IONIC COMPOUNDS

  • Salt: constituent ions form solid crystal lattice, high MP, dissolves in H2O to give cations (+) and anions (-) surrounded by polar H2O molecules (Fig 11.1)

  • Acid: produces H+ in water, sour in taste

    • HBr  H+ + Br -

  • Base: produces OH- in water, bitter in taste

    • KOH  K+ + OH -


Acids 1

ACIDS (1)

  • Acids produce H+ cations in an aqueous soln.

  • Monoprotic acids give up to one H+ ion per acid (*HCl-hydrochloric, *HNO3-nitric, HBr-hydrobromic)

  • Diprotic acids give up to two H+ ions per acid (*H2SO4-sulfuric).

  • Triprotic (H3PO4-phosphoric).

  • See uses of acids on pp 420-421, 424-25

  • * You are using in lab


Acids 2

ACIDS (2)

  • All acids on previously slide but phosphoric acid are strong acids meaning they ionize completely in water.

    • HBrH+ + Br -strong acid; every HBr ionizes. We say that the reaction is complete meaning essentially no reactant exists.


Acids 3

ACIDS (3)

  • Weak acids do not ionize completely.

    • HF ↔H+ + F -weak acid

    • Only 1 per 100 HF ionizes. We say that HF and its constituent ions are in equilibrium meaning both reactants and products exist in balance.

    • Other weak acids: HNO2-nitrous, H2SO3-sulfurous, phosphoric, organic acids


Molarity 1

Molarity (1)

  • Concentration unit reflecting amount of solute in solvent

  • Molarity = M = mole solute/liter soln

  • Mole = number of 12C atoms in exactly 12 g of 12C = Avogadro’s number = 6.02E23

  • Let’s consider concentration of H+ ions in water = [H+]. 1 g H+ = 1 mol H+

  • Also 1 liter = 1 L = 1000 mL


Molarity 2

Molarity (2)

  • 0.001 mol [H+] in 1 L soln has a molarity of 0.001 mol/1 L = 0.001 M or 1E-3 M.

  • 0.000001 mol [H+] in 0.1 L soln is 1E-5

  • 5E-3 mol [H+] in 1 L soln is 5E-3 M

  • 2.34E-4 mol [H+] in 1 L soln is 2.34E-4 M

  • 4E-8 mol [H+] in 0.5 L soln is 8E-8 M

  • Ex 11.4: 0.050 g H+ in 0.50 L yields [H+] = 0.050 mol/0.50 L = 0.1 M


Ph scale

pH SCALE

  • Another way to describe [H+] is to use the pH scale where molarity is expressed as 1.0 x 10-pH. Note that pH is the negative of the exponent meaning that pH is positive.

    • 1E-3 M has pH = 3

    • 1E-5 has pH = 5

    • 5E-3 M = 1E-2.30 M has pH = 2.30

    • 2.34E-4 M = 1E-3.63M has pH 3.63

    • 8E-8 M = 1E-7.10 M has pH = 7.10


Ph scale 3

pH SCALE (3)

  • The pH scale goes from 1 to 14 corresponding to10-1 M (very high [H+]; pH = 1) to 10-14 M (very low [H+]; pH = 14).

  • pH = 7 is a neutral solution

  • pH < 7 means acidic

  • Figure 11.9


Bases

BASES

  • Bases produce OH- anions in an aqueous soln

  • OH- anion is the hydroxide ion

  • Strong bases ionize completely

    • LiOH Li+ + OH-

  • Weak bases ionize to a small degree

    • Ca(OH)2↔Ca2+ + 2OH-

    • NH3 + H2O↔NH4+ + OH-

    • CO32- + H2O↔HCO3- + OH-

  • Uses on pp 428-430


Ph and bases

pH and Bases

  • If [H+] > 1.0E-07 M or pH < 7, solution is acidic

  • If [H+] < 1.0E-07 M or pH >7, solution is basic

  • In an aqueous soln, [H+] x [OH- ] = 1.0E-14

  • Pure Water has [H+] = [OH- ] = 1.0E-07, is neutral and has a pH = 7

  • Figure 11.9


Ph and plants

pH and Plants

  • pH Affects Nutrient, Minerals and Growth

    http://www.esf.edu/pubprog/brochure/soilph/soilph.htm

    Antacids


Acid base neutralization 1

ACID-BASE NEUTRALIZATION (1)

  • H+ + OH- ↔ H2O

    • An equilibrium is established

    • Neutralization

    • Self ionization 

  • Acid + Base  Salt + Water

    • HCl + NaOH  NaCl + H2O


Hyponatremia

Hyponatremia

  • Duluth News-Tribune

  • The Pittsburgh Channel Feb 4, 2005

  • Water of Life, Water of Death http://www.mashinc.org/resources-essay-water.html

  • Acid-Base Balance

    http://www.e-kidneys.net/acidbase.html


Gatorade

Gatorade

  • Development of Gatorade http://www.rgp.ufl.edu/publications/explore/v08n1/gatorade.html

  • Chemistry and Gatorade http://chemcases.com/gatorade/


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