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P.Sci.Unit 11 Cont.

Solutions, Acids, and Bases

Chapter 8

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Acids and Bases

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Acids• Contain at least one hydrogen

atom that can be removed when the acid is dissolved in water. These form hydronium ions, H3O+.

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Properties of Acids• H+ ions interact with water

molecules to form H3O+ ions.• Taste sour.• Have a pH less than 7.• Are electrolytes because in solution

they contain ions.

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Properties cont.• Are corrosive and can cause severe

burns.• Reacts with indicators to produce a

change in color (litmus turns red).• Neutralize bases to form a salt and

water.

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Bases• Forms hydroxide ions (OH-) in a

water solution.

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Properties of Bases• Many are crystalline solids.• Feel slippery.• Have a bitter taste.• Have a pH of greater than 7.• Are electrolytes because in

solution they contain ions.

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Properties cont.• Are corrosive and can cause severe

burns.• Reacts with indicators to produce a

change in color (litmus turns blue).• Neutralize acids to form a salt and

water.

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Strength of Acids and Bases• The strength of an acid or base

depends on how completely a compound separates into ions when dissolved in water.

• Ions can carry an electric charge so a strong acid will carry more electricity than weak acid.

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Strength of Acids• Acids that ionize

almost completely in a solution is a strong acid.

• Ex: HCl, HNO3, and H2SO4

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Strength of Bases• Bases that dissociate completely in

a solution is a strong base• Ex: NaOH

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Strength vs. Concentration• Strong and weak – tells how easy the

acid or base dissociates in solution. • Concentration – The amount of acid

or base in a solution – • It is possible to have a dilute

concentration of a strong acid that would be less harmful than a concentrated weak acid.

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pH• pH means potential of hydrogen • It is a measure of the concentration

of H+ ions. • The greater the concentration of H+

the lower the pH. The lower the pH – the stronger the acid.

• The pH range goes from 0 – 14

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• To determine the pH of a solution an indicator is used (an organic compound that changes color in the presence of an acid or base.)

Strong Acid Neutral Strong Base0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

pH scale

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Salt• Neutralization is a chemical reaction

between an acid and a base that takes place in a water solution. Salts are formed when the negative ion from an acid combine with the positive ions from a base.

Acid + base → salt + water• Salt (NaCl) is essential for most

animals

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