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Acids, Bases and Salts

The magic acid, a super acid that dissolves hydrocarbons: The Magic acid - a super acid that dissolves hydrocarbons! The acids, which are stronger than 100% sulfuric acid, are known as super acids. Magic acid is the world's strongest super acid. Which is a mixture of fluoro-sulfuric acid and antimony pentafluoride (HSO3F−SbF5). Magic acid is not just a fancy name; it has more than a few amazing properties such as its ability to protonate and dissolve hydrocarbons.
The interesting story behind discovery and naming of this acid is: On a Christmas party in Professor George Olah laboratory, a candle left over from the cake was placed in the chemical compound we now know as Magic acid, and the candle disappeared like magic right before their eyes. A quick trip to the NMR revealed that the parafin wax (hydrocarbon – poor proton acceptor) was now a tert–butyl cation solution. The saturated hydrocarbons had been protonated! Professor Olah used this super acid (Magic acid) in his innovative research of carbocation chemistry, and became the sole recipient of the Nobel Prize in Chemistry in 1994.

Learning Objectives

After completing the topic, the student will be able to:

  • Define the terms acid, base, amphoteric substance and salt.
  • Classify the substances into acids, bases, amphoteric substances and salts.
  • Differentiate the properties of acids and bases.
  • Appreciate the various theories developed to describe acid base behavior of substances.
  • Define pH and express the strength of an acid or base on pH scale.
  • Understand the phenomenon of salt hydrolysis and know the significance of buffers.
  • Know the procedure involved in acid–base titrations, solve the problems based on acid–base titrations.
  • Plot and describe the titration curves.
  • Know the principle involved in using the indicators in acid – base titrations. Discuss the application of acids and bases.
Effect of acidic and basic conditions on floral colors Effect of acidic and basic conditions on floral colors Flower color in Hydrangea macrophylla is dependent on pH values of the soil. Blue flowers will be produced in acidic soil (pH 5.5 and lower), whereas neutral to alkaline soils (pH 6.5 and higher) will usually produce pink flowers. Between pH 5.5 and pH 6.5, the flowers will be purple or a mixture of blue and pink flowers will be found on the same plant.
Introduction

Acids and bases are important in numerous chemical processes that occur around us, from industrial processes to biological ones, from reactions in the laboratory to those in our environment.

The time required for a metal object immersed in water to corrode, the ability of an aquatic environment to support fish and plant life, the fate of pollutants washed out of the air by rain, and even the rates of reactions that maintain our lives are all critically dependent upon the acidity or basicity of solutions. Indeed, an enormous amount of chemistry can be understood in terms of acid–base reactions.

From the earliest days of experimental chemistry, scientists have recognized acids and bases by their characteristic properties. Acids have a sour taste (for example, citric acid in lemon juice) and cause certain dyes to change color (for example, litmus turns red on contact with acids). Infact, the word “acid” comes from the Latin word acidus, meaning sour or tart. Bases, in contrast, have a bitter taste and feel slippery (soap is a good example).

The word “base” comes from an old English meaning of the word, which is “to bring low”. When bases are added to acids, they lower the amount of acid. Indeed, when acids and bases are mixed in certain proportions, their characteristic properties disappear altogether forming a new substance commonly called as "salt" .

Strange form of color and salt in Dead sea Strange form Dead Sea! The extreme salt concentration prevents any kind of macroscopic aquatic life such as fish and plants to flourish here, though minuscule quantities of bacteria and microbial fungi are present. The water of the lake is so dense that it is impossible to sink in the Dead Sea.
Formation of salt from an acid-base reaction

Salt is the ionic product of an acid‐base reaction. In everyday language, the word salt implies sodium chloride, NaCl, table salt. In the language of chemistry, however, salt is a general term meaning any ionic compound formed from the reaction between an acid and a base. Hydrogen chloride and sodium hydroxide, for example, react to produce the salt sodium chloride and water:

Salt implies Sodium chloride

Seawater is salty and we obtain this salt, by evaporating sea water in salt pans. The salt obtained from seawater is not pure sodium chloride (NaCl), but contains many other salts in smaller proportion. These are KCl, KI, MgI2, MgCl2 etc. These are salts of other metals like potassium and magnesium. They are formed when alkalis like KOH and Mg(OH)2 react with acids like HCl or HI etc. Metal atoms donate electrons and form positive ions. So, they can replace hydrogen ion from an acid and make the respective salt. The OH of the base combines with H+ of an acid and forms water.

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