Greater Minds Tutors

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) <----...

Introduction Growing up, we used to think that any substance that burns is an acid, until we learnt about acids, bases and salts in our foundational chemistry class. It was then clear to us that there is more to acids than corrosivity, and not every substance that is corrosive, is an acid. Definition The definitions of an acid is based on three different concepts of acid-base reactions, namely the Lewis, Brønsted-Lowry and Arrhenius concepts. Lewis Acids According to G. N. Lewis, in acid-base reactions, the reactants undergo co-ordinate covalent bonding, in which one reacting species has the ability to accept a lone pair of electrons, while the other can readily donate a lone pair of electrons. A Lewis acid is an electron pair acceptor, because it has an empty orbital. Examples are H+, H3O+, Cu2+, Fe3+. Brønsted -Lowry Acids According to J. H. Brønsted and M. Lowry, an acid-base reaction involves the transfer of proton from one of the reactants to the other. A Brønsted-Low...

Half-life of a Reaction The half-life, t1/2, of a reaction is the amount of time it will take the concentration, [A], of a reactant to reduce to half its initial concentration, [Ao]. That is to say,               @ t1/2, [A] = [Ao]/2 ...……(i) The half-life of the various orders of reaction can be calculated by substituting the above equation into the respective integrated rate laws. ( a) Half-life of a Zeroth-Order Reaction Recall that the zeroth-order integrated rate law is given by:                  [A] = [Ao] - kt …………(ii)                  [Ao] - [A] = kt @ t1/2, [A] = [Ao]/2                  kt1/2 = [Ao] - ([Ao]/2)          ...

In our previous post, we looked at the overview of the rates of chemical reactions, where we studied the concepts and factors that affect the rates of reactions. In this post, we will be studying the rate law and the different orders of reaction, and how to determine them. Rate Law Consider the reaction:             mA + nB ----> Products The rate law states that the rate of a reaction is directly proportional to the active masses of the reactants. This implies that the concentration of the reacting species will determine how fast and how far a reaction can go. Using the above equation, the rate law can be expressed as:             rate & [A]^m[B]^n ..........(i)             rate = k[A]^m[B]^n ..........(ii) where, [A] = concentration of reactant A [B] = concentration of reactant B    & = sign ...

By Charles Offiong A few days ago, I was discussing with a childhood friend of mine, who also doubled as my classmate. Our subject of discussion was the state and quality of our education vis-a-vis what was obtained in our days. We were lucky to attend one of the foremost secondary schools in Nigeria, the Hope Waddell Training Institution, Calabar, founded in 1895, which prided itself as the oldest in South-Eastern Nigeria and one of the best in West Africa. Apart from her, our first generation universities were ranked among the best in Africa. However, considering the current circumstances, it will be foolhardy of me to presume that my alma mater and those other institutions still maintain these bragging rights... The importance of education to our national development and its need to occupy the pole position of any government cannot be overemphasized. The talk about the declining standards of the Nigerian education is what the blind had seen the dumb told the deaf, so it is no long...

In our last post, we looked at the overview of electrode potentials, where we discussed metal ions/metal systems or half-cells, standard electrode potential and electrochemical cells in depth. Here, we will focus on the calculations involving electrode potentials, which include calculations of  the electromotive force (e.m.f) of electrochemical cells ,  the relationship between e .m.f & free energy and the relationship between e .m.f & equilibrium constant. Half-Cell Reactions                      Std Reduction Potential , E° (V) K+(aq) + e- <----> K(s)                              -2.92 Ca2+(aq) + 2e- <----> Ca(s)               ...