ACIDS

1. ACIDS

2. Acids • Can be defined as compounds that yield and donate hydrogen ions in water solution. • Bronsted defined acid as a substance that donates protons • Hydrogen ion results when a hydrogen atom loses its only electron, leaving a single proton • So both definitions say the same thing i.e. hydrogen ion is a proton

3. Acids • It is the hydrogen ions that are responsible for the particular properties of acids • Strong acids are completely ionized in solution and weak acids are partially ionized in solution. • Hydrochloric acid, nitric acid and acetic acids are called monoprotic acids • Because each yield one hydrogen ion in solution • Sulfuric acid is an example of diprotic acid. it yields 2 hydrogen ions per molecule.

4. Acids • Sulfuric acid is a strong electrolyte .It undergoes complete ionization. • Phosphoric acid is a tripotic acid • Hydrogen ions are too reactive to exist in solution by themselves. • They react with water to form hydronium ions. • When acids react with certain compounds these compounds change in color. • Substances that change in color in the presence of acids are called Indicators.

5. Acids • One of the most common indicators for acids is litmus. • Blue litmus turns red in the presence of an acid in the presence of an hydrogen ion. • Another common indicator phenolphthalein turns from red to colorless in the presence of an acid. • Acids react with metal oxides and hydroxides to form water and a salt…

6. Acids • Hydrogen is classified with the metals • Any metal above hydrogen in the activity series will displace the hydrogen from an acid. • Acids react with any metal above hydrogen in the activity series to produce hydrogen gas and a salt. • These are examples of single replacement reactions • The metal replaces the hydrogen in the acid

7. Acids • Thus acids cannot be stored in containers made up of active metals. • Acids are usually stored in glass or plastic containers. • Reactions involving acids are usually carried out in glass or plastic containers • Reactions involving acids are usually carried out in glass or plastic containers.

8. Acids • Since any metal below hydrogen in the series should not be able to replace a hydrogen from an acid, • So we expect the mixing of copper with hydrochloric acid to produce no hydrogen, and it does not.

9. Uses of acids • Acids such as hydrochloric acid are used in industry and in laboratory work in large amounts. • Hydrochloric acid normally found in the gastric juices is necessary for the proper digestion of proteins in the stomach.

10. Buffers • The PH of pure water is 7.0 which is neutral. • If an acid is added to water, the PH goes down. • How far below 7 it goes down depends on how much acid and how strong an acid is added. • When a base is added to pure water, the PH rises above 7.0

11. Buffers • However when small amounts of acid or base are added to a buffer solution, the PH does not change appreciably. • A buffer solution is defined as a solution that will resist changes in PH on addition of small amounts of either acid or base. • Buffer solutions or buffers are found in the body fluids and are responsible for maintaining the proper PH of those fluids. • The normal PH range of blood is 7.35-7.45 and even a slight change in PH can cause a very definite pathologic condition.

12. Buffers • When PH falls below 7.35 the condition is known as acidosis. • When the Ph of blood rises above 7.45 the condition is known as alkalosis. • A buffer solution consists of a weak acid and salt of a weak acid. • There are some buffer systems in the blood. • One of these consists of carbonic acid H2C03, a weak acid and sodium bicarbonate ( NaHC03), the salt of a weak acid.

13. Buffers • Suppose that an acid such as HCl enters the bloodstream, the HCl reacts with the NaHCO3 part of the buffer according to the reaction. HCl + NaHCO3 → NaCl + H2CO3 • The Nacl produced is neutral, it does not hydrolyze. The H2CO3 is part of the original buffer system and is only slightly ionized. • In the body, acids are produced by various metabolic processes. • When these acids enter the bloodstream, they are removed by this reaction or a similar reaction.