Acidity and Basicity

E X P E R I M E N T 11

Introduction Acidity and Basicity

Acids

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Any solution that releases hydrogen ions when added to water and has a pH of less than 7.0 

 pH  –  it measures measures the acidity of of a liquid by measuring the concentration concentration of hydrogen ions.

PROPERTIES OF ACIDS : 

Sour taste

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Litmus paper blue turns red

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Reactions with metal oxide and hydroxide

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Neutralize bas forming water 

Bases

Substances which combines with acid and also known as Alkaline substance.  Compound that furnishes the hydroxide ions.  Compound that gives or donate hydroxyl ions in water or other substances. 

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Hydroxyl  –  unit that composed of one or  more atom of hydrogen and one of  oxygen.

PROPERTIES OF BASES : 

Slippery

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Soapy feeling and a biting , bitter taste

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Red litmus blue , turn methyl organic from red to yellow

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Turn phenolphthalein from colorless to red

Procedures Acidity and Basicity

Using the pH Paper 

pH paper in test solution • Dip • For 10 seconds

Color Chart • Match the color  obtained in the test sol’n

Record

Repeat • With other  test solutions

Using the pH Meter 

Buffer Solution • Immerse the electrode • After that, rinse the electrode with distilled water  • Wipe with tissue

First Solution • Dip the electrode • Get the pH reading • Record

Distilled Water • Rinse the electrode • Wipe it with tissue paper 

Repeat • With other test solutions

Keep the electrode immersed in distilled water when not inuse .

Samples

Chemical Formula

Structural Formula

Functional Group

CH3COOH

Carboxyclic Acid

Monochloroacetic acid

ClCH2COOH

Carboxyclic Acid, Alkyl Halides

Acetone

(CH3)2CO

Ketone

Acetamide

CH3CONH2

Amides

Acetic Acid

Chemical Formula

Glysine

NH2CH2COOH

Structural Formula

Functional Group Amines, Carboxyxlic Acid

Lysine

C6H14N2O2

Amines, Carboxyxlic Acid

Isopropyl Alcohol

(CH3)2CHOH

Alcohol

Phenol

C6H5OH

Alcohol, Aromatic Compound

Chemical Formula

Commercial Vinegar 

C2H4O2

Calamansi Juice

C6H8O7

Spoiled Milk

C3H6O3

Structural Formula

Arrhenius Concept Acidity and Basicity

 Svante Arrhenius , a Swedish chemist who received a Nobel prize in i n 1903 for his work  on electrolytes, focused on what ions were formed when acids and bases dissolved in water.

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One of the properties that acids and bases have in common is that they are electrolytes--they electrolytes-they form ions when they dissolve in water.  He came up with the concept or idea that acids dissociated in water to give hydrogen ions (H+) and that bases dissociated in water to give hydroxide ions. (OH-) 

Examples: HCl

H+ + Cl-

An acid, like HCl, is something that dissociates in water to give hydrogen ion. NaOH

H+ + Cl-

A base, like NaOH, is something that dissociates in water to give hydroxide ion.

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Arrhenius focused on the idea that acids and bases split into ions when they dissolved in water.

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In a sense, the Arrhenius concept focuses on what the chemical contains or  or what what is there in solution.

Brønsted-Lowry Concept Acidity and Basicity

With the Brønsted-Lowry concept we usually refer to a hydrogen ion as a proton.  That is because a proton is all that is left when a hydrogen atom loses an electron to become an ion. 

Brønsted Acids Proton (H+) Donor.  When an acid reacts, the proton is transferred from one chemical to another.  The chemical which accepts the proton is a base. 