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# Acids and Bases Help (page 3)

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### Strengths of Acids and Bases

As shown in Table 14.3 , acids and bases have different strengths and weaknesses. Some mild acids like water (remember, it provides a proton) can be used to wash your hands of dirt. You couldn’t use sulfuric acid for the same purpose.

Table 14.3 Many foods and household solutions are strongly acidic or basic.

The strengths of acids can be found by how well they ionize. If two acids react with a certain solution, generally one will be ionized more than the other. Just as people are all individuals, elements have strengths and weaknesses too. Reactions usually go in the direction of the weaker acid or weaker base. A stronger acid will be transformed into products that include a weaker acid. The same is usually true of reactions with bases.

One exception happens in the presence of water. Water bends the rules. In water, strong acids seem to have the same strengths. They ionize well and seem to “even up” the differences.

You may see the words conjugate acids and conjugate bases . A conjugate acid is the part of an acid-base reaction that donates the proton. A conjugate base is the part of the joined compound that can accept a proton.

Strong acids have weak conjugate bases. Strong bases have the weakest conjugate acids.

The strength of acids and bases is based on the amount of hydronium ions (H 3 O + ) and their concentration in a solution. The pH meter records this concentration with strong acids ranging from 2.0 to 5.0, neutral pH being a pH of 7.0, and strong bases ranging in values from 8.5 to 10.0. The lower the pH number, the stronger the acid; the higher the pH number, the stronger the base.

There are two clues to figuring out the strength of an acid:

1. Check the polarity of the H + bond. The more polar the bond, the more easily the H + proton is removed and the stronger, more interactive the acid.

2. Check the size of the atom bonded to the H + .

Commonly, you will find that the larger the atom, the weaker the bond and the stronger the acid. When hydrogen bonds to chlorine, or bromine, the larger molecule with greater orbitals has more interactivity. When comparing the acids HF, HCl, HBr, and HI, the acidity increases as the size of the atoms increases. So they can be arranged as HI > HBr > HCl > HF > H 2 O.

The strength of bases can be found in much the same way. Stronger bases ionize almost completely in water, while weak bases do not. This happens because less ionized bases do not have free orbitals to allow the acceptance of additional protons. (Everybody is comfortable and stable and resists change.) A stronger base is able to accept H + more easily than a weaker one because it goes into the ion state more easily. The following bases can be arranged by strength OH > NH 3 > HCO 3 > C 2 H 3 O 2 > NO 3 > HSO 4 .

Practice problems for these concepts can be found at –  Acids and Bases Practice Test

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