Acids and Bases

With our understanding of strong, weak, and non-electrolytes we can now examine the Arrhenius Definition of Acids and Bases:

Acids:
Substance that produces H+ ions when it is dissolved in H2O.
Bases:
Substance that produces OH- ions when it is dissolved in H2O.

For example, HCl is an acid,

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and NaOH is a base,

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Acids and Bases that are strong electrolytes are called Strong Acids and Strong Bases, respectively. Acids and Bases that are weak electrolytes are called Weak Acids and Weak Bases, respectively.

Strong Acids

HCl is an example of a strong acid:

HCl(aq) H+(aq) + Cl-(aq)

Other examples include HBr, HI, HClO4, HClO3, H2SO4, and HNO3.

Weak Acids

HF is an example of a weak acid:

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Other examples include HC2H3O2, H2CO3, H2SO3, H3PO3, and H3PO4. The last four are examples of polyprotic acids. These are acids that can produce more than one H+ ions when dissolved in water. H2CO3 and H2SO3 are called diprotic acids, and H3PO3 and H3PO4 are called triprotic acids. HF, HCl, HBr, and HC2H3O2 are examples of monoprotic acids. The dissociation of polyprotic acids usually occurs in steps. For example, only after H3PO4 loses its first H+ ion will it lose its second H+ ion, and then it will lose its third.

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In this example, all three species H3PO4, H2PO4-, and HPO42- are weak electrolytes so H3PO4 is considered to be a weak acid. H2SO4 is another example of a diprotic acid. In the case of H2SO4 the first H+ ion is produced readily so the species H2SO4 is considered to be a strong electrolyte (i.e. strong acid). The species HSO4-, however, is a weak electrolyte.

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Strong Bases

NaOH is an example of a strong Base:

NaOH(aq) Na+(aq) + OH-(aq)

Other examples include LiOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, and Ba(OH)2.

Weak Bases

Ammonia, NH3, is a good example of a weak base.

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Other examples include C6H5N (pyridine) and C6H5NH2 (aniline).

Homework from Chemisty, The Central Science, 10th Ed.

4.1, 4.3, 4.5, 4.7, 4.9, 4.11, 4.13, 4.15, 4.17, 4.33, 4.35, 4.37,