a. What is a transition element?
b. Consider the electron configuration of the following elements: A=2, 8,6; B=2,8,2; C=2,8,1, D=2,8,8
State the element which forms a: i. doubly charged cation; ii. soluble trioxocarbonate (IV).
c. Explain briefly why there is a general increase in the first ionization energies of the elements across the period in the periodic table.
d. Give two examples of an aliphatic compound
e. Explain briefly why alkanols are stronger bases than water.
f. State the major raw materials used in the Solvay process
g. What is geometric isomerism?
h. Give a reason why water gas is a better fuel than producer gas.
i. Define the term heat of combustion.
ji. State Faraday’s second law of electrolysis
ii. Calculate the amount of silver deposited when 10920 coulombs of electricity is passed through a solution of a silver salt.
[IF = 96500 C mol-1]
Explanation
a. A transition element is one which has incompletely filled d-orbitals.
bi. B
ii. C
c. Across a period(from left to right) there is a gradual increase in the number of protons in the nucleus/effective nuclear-charge.
This increases the force of attraction between the nucleus and the electrons hence more energy is needed to remove the outermost electron.
d. -methane
-ethene
-ethyne
-ethanol
-ethanoic acid
e. -Alkanols are formed by replacing one hydrogen of water by an alkyl group
-Alkyl groups have a positive inductive effect/ are electron releasing/electron donating
-This increases the electron density of the oxygen
f. -NaCl
-CaCO3
-NH3
-C
g. Geometric isomerism is the existence of two compounds with the same molecular formula but differ in the arrangement of groups attached to the carbon-containing double bond
h. This is because constituents of water gases(CO and H2)are both combustible and give a higher calorific/heat value than producer gas
i. It is defined as the heat change/released when 1 mole of a substance is burnt in excess oxygen.
OR It is defined as the heat change/released when 1 mole of a substance is completely burnt in air
ji. When the same quantity of electricity is passed through different electrolytes, the relative number of moles of the elements discharged is inversely proportional to the charges on the ions of the element.
ii. 96500 C liberates 1.0 mol of Ag(s)
10920 C will liberate 10920/96500
=0.113 mole