What are acids??? <ul><li>Any of a group of chemical compounds with certain similar properties. </li></ul><ul><li>A compound which, when dissolved in water, produces a hydrogen ion, H + (aq) as the only positive ion. </li></ul><ul><li>A compound containing hydrogen which may be replaced directly or indirectly by a metal. </li></ul><ul><li>Have a variety of properties, but all these properties are derived from a single type of behavior. This behavior is the production of the hydrogen ion (H + ). </li></ul>
Action on litmus paper? Turn blue litmus to red. Acid has a pH range which >7 Some of the weaker acids, however, for example carbonic acid, are so feebly acidic that they can only turn litmus to claret color. Acids contain combined hydrogen. When a sample of zinc, a fairly reactive metal, is dropped into a test tube containing a acid such as HCl m a reaction occurs. The bubbling in the tube indicates that a gas is released. When we test this gas by inserting a burning splint into the test tube, the gas burst into flame and produces a small popping sound. This is the characteristic test for hydrogen gas. In general, when certain acids react with metals, hydrogen gas is released. Metal + acid metal salt + hydrogen Reaction with carbonates Form salts, water and carbon dioxide gas. Example: Na 2 CO 3 (s) + 2HCl 2NaCl (aq) + CO 2 (g) + H 2 O Properties Of Acids: Taste? Sour. This is true of the three common mineral acid, sulphuric acids, hydrochloric acids, nitric acids and others. The sour taste of many unripe fruits, lemons and sour milk is cause by the acids in them. Corrosive action Most people connect the term acid with the idea of a corrosive, “burning” liquid. Two of the commonest acids- sulphuric acid and nitric acid- are actually corrosive liquids. Acids are not, however, generally corrosive and most of them are solids. Acids release hydrogen in water solutions. When an acid dissolves in water, the acid ionizes, releasing both hydrogen ions and ions of a non-metal or non metallic polyatomic ion. Thus, when hydrochloric acid is dissolved in water, the acid ionizes, forming hydrogen ions and chloride ions, as shown in the following equation: HCl (aq) H + (aq) + Cl 1- (aq) other examples: H z SO 4 (aq) 2H + (aq) + SO 4 2- (aq) H 3 PO 4 (aq) 3H + (aq) + PO 4 3- (aq) * Thus acids are defined as substances that release hydrogen ions in solution. It is these H + (aq) are responsible for the properties of acids. Reaction with bases: Form salts and water. Another word: neutralization. Ionic equation: H + + OH - H 2 O Example: HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O (l)
The reactions of the three common inorganic acids with various metals.
Inorganic acids???? <ul><li>Can be prepared in laboratory from mineral elements and inorganic matter. </li></ul><ul><li>In general, they do not contain carbon atom. </li></ul><ul><li>They are strong acids. </li></ul><ul><li>They are widely used in the production of other chemicals, explosive, fertilizers, metals, paints, plastics and synthetic fibers and in refining of petroleum. </li></ul>Common inorganic acids:
<ul><li>Dilute sulphuric acid or Hydrochloric acid (HCl) helps to remove rust in painting. </li></ul><ul><li>Baking powder contains tartaric acid. </li></ul><ul><li>Medicines. </li></ul><ul><li>In industries. </li></ul><ul><li>Manufacture of fertilizers, plastics , photographic films and dyes. </li></ul><ul><li>To clean brick and tile. </li></ul><ul><li>Used in the manufacture of food products such as sugar. </li></ul><ul><li>Used in the manufacture of glue. </li></ul>
What is base? <ul><li>A substance that will react with acids to form salt and water. </li></ul><ul><li>A substance which can combine with a hydrogen ion, H + (aq). The reactions are reversible. </li></ul><ul><li>Soluble base= alkali Insoluble base= metal oxides that carry the O 2- ions. </li></ul><ul><li>Chemists often define a base as any chemical compound that yields hydroxide ions (OH-) when dissolved in water. </li></ul><ul><li>A base also may be defined as a chemical substance that readily combines with a proton . </li></ul><ul><li>However, a base is most broadly defined as a substance that provides a pair of electrons to form a chemical bond. Under this definition, some chemicals that do not contain hydroxide ions are also classified as bases. </li></ul>Bases that are soluble usually contain metallic cations from group 1 and group II metals. Oxides containing transition metals or group III metals are usually insoluble or partially soluble.
Properties of base: Feel slippery/soapy. If you rub a drop or two of household ammonia between your fingers, you may experience the slippery feeling of a base. Wet soap is also slippery because of the presence of a base. Turn red litmus to blue. A common indicator, used to detect the presence of a base, is phenolphthalein which, when mixed with a base, turn pink. Reaction with ammonium salts: When a mixture of an ammonium salt and an alkali is heated, ammonia gas is given off. The reaction may be briefly summarized as : OH - + NH 4 + NH 3 + H 2 O Example: NH 4 Cl (s) + NaOH (aq) NaCl (aq) + NH 3 (g) + H 2 O(l) Precipitation of metal hydroxides: Solutions of metal hydroxides are used to precipitate insoluble metal hydroxides from solutions of their salts. Example: 2NaOH(aq) +CuSO 4 (aq) Cu(OH) 2 (S) + Na 4 SO 4 (aq) <ul><li>Reaction of alkalis with metals is limited. Strong alkalis such as Sodium Hydroxide can sometimes react with aluminum to give hydrogen gas, similar to that of an acid reaction. </li></ul><ul><li>Strong alkalis are those with a higher pH value. Hence they are more reactive, with the ability to give away OH - ions for chemical reaction. </li></ul>
Classification of oxides: <ul><li>4 kinds of oxides: </li></ul><ul><ul><li>acidic </li></ul></ul><ul><ul><li>Amphoteric </li></ul></ul><ul><ul><li>Basic </li></ul></ul><ul><ul><li>Neutral </li></ul></ul>Metal oxides are basic (e.g. copper (II) Oxide, iron (II) oxide). These oxides have the properties to that of an acid when they dissolve in water. Oxides are formed when metallic and non-metallic elements burn in oxygen. There are some neutral oxides as well. They are the non-metallic oxides, (e.g. carbon monoxide, water, Nitrogen oxide .) Some oxides are atmospheric in nature (e.g. aluminum oxide, zinc oxide). These oxides show both acidic and basic properties.
<ul><li>Sodium Hydroxide used in household drain cleaner. </li></ul><ul><li>Potassium Hydroxide used in soap making. </li></ul><ul><li>Magnesium hydroxide used in antacid. </li></ul><ul><li>Ammonium hydroxide (ammonia)is used as a cleaning agent </li></ul><ul><li>Calcium hydroxide (slaked Lime/lime water) used in lab for Carbon dioxide test. </li></ul>
What is salt? Many chemical compounds may classified as salt. The most familiar to all of us is the table salt. In general, salts are ionic compounds that are composed of metallic ions and non-metallic ions. For example, sodium chloride is composed of metallic sodium ions and non metallic chloride ions. Salts can be considered to be formed by the reaction of an acid with a base. Salts are classified into neutral, basic or acidic according to the effect they have on pH when dissolved in water. Strong acid + strong base neutral solution Weak acid+ strong base base solution Strong acid +weak base acidic solution
<ul><li>Salts dissociate in water. </li></ul><ul><li>Consist of tightly bonded ions. In water, these bonds are weakened and the ions become mobile. This accounts for the fact that solutions are generally electrolytes. In water, for example , sodium chloride ionizes or dissociates like this: </li></ul><ul><li>NaCl (s) Na 1+ (aq) + Cl 1- (aq) </li></ul><ul><li>salts may also react with water. </li></ul>Color? Exist in all different colors. For examples: sodium chloride =transparent Nickel oxide=green Potassium dichromate=orange Taste? Different salts can elicit all the five basic tastes. Odor? Depend on the acid and base which make up the salt.
Methods of preparing salts: <ul><li>Crystallization for soluble salts </li></ul><ul><li>Precipitation for insoluble salts </li></ul><ul><li>Titration method </li></ul>
Examples and uses of salts: <ul><li>Ammonium chloride: </li></ul><ul><li>Used in soldering , as electrolyte in dry cells. </li></ul>Sodium bicarbonate: Used in baking powder, in manufacture of glass. Sodium chloride: Used for seasoning and preserving food, essential in life processes Calcium chloride: Used as a drying agent to absorb moisture, in freezing mixtures. Silver bromide: Used in making photographic film. Potassium nitrate: Used in manufacture of explosives, fertilizers Sodium nitrate: Used in fertilizers ; source of nitric acid