Acids & Bases

• red - acid

• blue - base

• acid-base indicators

• Arrhenius - all acids contained H atoms that became H+ ions in water. Bases released OH- ions into water.

• Water will want to establish an equilibrium H+ ions react with OH- ions to form water molecules. Water molecules react to form H+ ions and OH- ions.

• But what about ammonia which acts as a base but does not contain the hydroxide ion?

• Bronsted theory - proposed that acids and bases be identified by their behavior in a reaction

• A Bronsted acid is a proton (H+) donor

• A Bronsted base is a proton acceptor

• There are two acids and two bases

• When an acid donates a H+, a base is left.

• pH = "potential hydrogen" a measure of how many hydrogen ions exist in a solution.

• the pH scale is primarily from 0 to 14

• A neutral solution has a pH of 7

• acidic solutions (0 to 6.9)

• basic solutions (7.1 to 14)

• Vinegar (acetic acid) great on salads, but using hydrochloric acid would be a bad idea.

• Maybe use it to clean bricks but not on food.

• Acids and bases are classified into one of two categories depending on their strength, which is the degree to which they form ions.

• Strong - completely dissociate or ionize in water ( NaOH & HCl)

• Weak - produce few ions when dissolved in water

Contains acids and bases with a wide range of strengths.

Most acids and bases fall into this category.

Only partially ionized

• Amino acids have properties of both weak acids & bases.

• The coiling of DNA is due to interactions between weak acids and bases.

• The combination of strength and concentration determine the behavior of a solution

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• Shampoos with high pH make the entire hair shaft swell and push the cells of the cuticle away from the rest of the shaft

• Harsh basic solutions dissolve some of the cuticles, damaging the hair (like in dye)

• Acidic substances (low pH) make the hair shaft tight and smooth by shrinking it and causing the cells of the cuticle to lie flat.

• Low pH shampoos help restore damaged hair and

• brighter skin - high pH

• Remove top layer of keratin which removes dead cells and the new cells will look fresh and vibrant.

• Occasional use is ok, but regular use may damage health skin by removing too many layers

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