Form 3 Paper 2 Term 2 2020 Chemistry Exam Set 13 [PDF]

The grid below forms part of the periodic table. Study it and answer the questions that follow. The letters do not represent the actual symbols of the elements.

1. Write the general name given to the element P belong.
2. An element N has an atomic number of 15. Write down its electronic arrangement and hence fix it in its right position on the grid above.
   Electronic arrangement
3. Compare the size of the atom of R and that of its ion. Explain your answer.
4. Give the formula of the compound formed between
   i. P and W
   ii. T and Y
5. Compare the melting points of element Q and S. Explain
6. State the least reactive element in the grid. Give a reason for your answer
7. Give two advantages that element S has over element Q in making electric cables
8. Draw a dot (.) and cross (x) diagram to represent the bonding in compound formed between T and Y

Study the table below and answer the questions that follow

Bond type	Bond energy Kjmol-1
C-C	346
C=C	610
C-H	413
C-Br	280
Br-Br	193

1. Calculate the enthalpy change for the following reaction
   C₂H_4(g) + Br_2(g) → C₂H₄Br_2(g)
2. Name the type of reaction that took place in above

Butane C₄H₁₀ cannot be prepared directly from its elements but its standard heat of formation (∆$H_{ʄ}^{\theta }$) can be obtained indirectly.
The following heats of combustion are given
∆$H_C^{\theta }$ (Carbon) = -393kJ/mol
∆$H_C^{\theta }$ (Hydrogen) = -286kJ/mol
∆$H_C^{\theta }$ (Butane) = -2877kJ/mol

1. Draw an energy cycle diagram linking the heat of formation of butane with its heat of combustion and the heat of combustion of its constituents elements.
2. Calculate the heat of formation of butane ∆$H_{ʄ}^{\theta }$ (C₄H₁₀)

Given that the lattice enthalpy of potassium chloride is +690kJ/mol and hydration enthalpies of K⁺ and Cl- are -322kJ and -364kJ respectively. Calculate the enthalpy of solution of potassium chloride.

The diagram below represents the Haber process for the manufacture of ammonia. Study it and answer the questions that follow.

1. Name any two impurities removed by the purifier.
2. The catalyst used in the process is finely divided iron. Why iron is finely divided?
3. In the Haber process the conversion of nitrogen and hydrogen into ammonia is only 10%. The remaining unreacted gases are recycled. What is the advantage of this?
4. A part from iron catalyst and pressure of 500 atmospheres, name any other condition required for this process.