(a)i. Define an acid according to the Lewis concept
ii. Give one example of a Lewis acid
(b) Explain salting out in soap preparation
(c) State the reagent and condition necessary for the following conversion
H−C≡C−H→Ag−C≡C−Ag
(d) What is the percentage abundance of an isotope?
(e)i. Why does the element with atomic number 18 not have an oxide?
ii. Explain why chlorine(I) oxide has a low melting point
(f). Describe a test to distinguish between concentrated HNO3 and concentrated H2SO4
(g) State two differences between an electrochemical cell and an electrolytic cell
(h) How does the trend in ionization energy affect the reactivity of group 1 elements?
(i).Define the term molecular formula
(j) State which of the gases H2 and NH3 would deviate more from ideal behaviour. Give reasons for the answer stated above
Explanation
(a)i. An acid is any compound which in a chemical reaction is able to attach itself to an unshared pair of electrons in another molecule-a base, to form a new compound
ii. - AlCl3
- BF3
- BeF2
- H+
- K+
(b). It is the addition of NaCl to the reaction mixture in soap production to facilitate the precipitation of soap from the mixture
(c) Reagent -- AgNO3 in NH3(aq) / Ammonical silver trioxonitrate
condition-- heat
(d) - It is the fraction of a given isotope in amixture of isotopes of the same element
- The % of an isotope with a specific atomic mass found in a naturally occuring sample of an element.
(e)i. Because the element is
- Unreactive
- Stable
- A noble gas
- Inert
- Completely filled outermost shell
ii. Because of weak forces between the molecules hence not much heat is needed to break the forces
(f) - (Conc) HNO3 produces brown fumes (of NO2) when copper tunings are added to it/copper (II) salt is added but H2SO4 will not react with the copper tuning/Copper (II) salt
- When Conc. H2SO4 is added to sugar it chars the sugar but Conc. HNO3 will not.
- Add BaCl2 solution to each acid white precipitate indicates H2SO4 no precipitate indicates HNO3
(g)
| Electrochemical cell | Electrolytic cell |
| anode is negative/cathode is positive | anode is positive/cathode is negative |
| reaction is spontaneous | non-spontaneous |
| chemical energy is converted to electrical energy | electrical energy is converted to chemical energy |
| current is generated from within the cell | current is generated from external source/battery |
| the two half cells are in separate containers and connected by a salt bridge | the two half cells are in the same container |
(h) Ionization energy decreases down group 1 elements, the lower the ionization energy, the easier to loose an electron hence the higher the reactive of the elements
(i) Molecular formula shows the actual number of atoms of each element in a molecule
(j) NH3 will deviate more because it has a larger volume and also it has a stronger intermolecular forces