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pH Chart In our last post: Types, Preparation & Uses of Salts , we studied that salts are the products of the neutralization reactions between acids and bases. Following this fact, all salts are expected to have a neutral pH of 7 in solution. Interestingly, some salts produce solutions with pH > 7 (basic solutions), while others produce acidic solutions with pH < 7. Such salts, which are the products of either weak acids and strong bases or strong acids and weak bases, decompose in water to form two products. This phenomenon is known as hydrolysis. Recall that from our post on pH in Acids & Bases (Part III) , we learnt that water contains equal concentration of hydrogen and hydroxide ions. Therefore, the dissolution of a salt in water is likely to upset this ionic equilibrium based on the salt's composition. This is the underlying principle of hydrolysis of salts. So, in this post, we shall be looking at the hydrolysis of different types of salts based on th

Introduction Before they are introduced to acids and bases, young chemistry students always think that sodium chloride (common salt) is everything there is to know about salts. However, from their knowledge of acids and bases, they also get to know about other substances, such as copper (II) tetraoxosulphate (VI), potassium trioxocarbonate (IV), ammonium chloride, calcium trioxonitrate (V) etc, which are classified as salts. These substances are the outcomes of the Arrhenius acid-base reactions. So, what is a salt? Definitions We will define a salt in terms of basicity (replaceable hydrogen ions) and neutralization. I) A salt is a substance formed when all or part of the replaceable hydrogen ions in an acid, are replaced by metallic ions (Na+, K+, Mg2+, Ca2+, Cu2+ etc) or ammonium ions (NH4+). This implies that every acid has its corresponding salts. The list below shows examples of some salts and their parent acids. 1. Acid : Hydrochloric acid (HCl) Salts : Sodium chloride

p H & pH Scale The pH (hydrogen ions potential) is a measure of the acidity or alkalinity of a solution. The concept of pH was introduced by Sörensén in 1909 to bring about the convenience of working with very dilute solutions. To this effect, he developed a scale consisting of fifteen numbers (0 - 14), which is used in pH meter, for measuring the relative acidity or alkalinity in solutions. This scale is known as the pH scale. The numbers in the pH scale are the values of the negative logarithms of the hydrogen ions concentrations in such solutions. From the above, we can define pH as the negative logarithm of the hydrogen ions concentration [H+] to base 10. Mathematically, this is given as: pH = - log [H+] ..........................(i) Alternatively, the above equation can be expressed as pH = log 1/[H+] .........................(ii) From equation (ii), we can also define pH as the logarithm of the reciprocal of the hydrogen ions concentration to base 10. The pH

In a layman's term, a base is the opposite of an acid. In other words, a base is everything an acid is not. Recall that in the Part I of this series, we looked at the definition of an acid using three different concepts. Similarly, we are going to define a base using the same concepts. Definition Lewis Bases According to G. N. Lewis, a base is any species that can readily donate a pair of electrons. The availability of lone pair(s) of electrons increases a substance's ability to behave as a base. Examples include H2Ö, ÑH3, Cl-, F- etc. They are also considered to be nucleophiles. Any species with an electron-rich centre is said to be a nucleophile. Brønsted-Lowry Bases According to Brønsted and Lowry, an acid is a proton donor, while a base is a proton acceptor. In other words, any substance that has the ability to accept a proton (hydrogen ion, H+) by donating a pair of electrons to it, is said to be a base. Examples are H2Ö, ÑH3, Br- etc. H2Ö(l) + H+(aq) <----&