Kcse Secondary Level Chemistry Form 2  Question Paper

Exam Name: Chemistry Form 2 

Course: Secondary Level

Institution/Board: Kcse

Exam Year:2010



1. An atom of element Z (not its actual chemical symbol) has 20 neutrons and 18 protons.

i. Deduce the symbol of the atom, including both the mass and the atomic numbers (2mks)

ii. To which group of the periodic table does Z belong to? (1mk)

iii. Identify element Z. (1mk)

iv. State and explain the chemical reactivity of the element Z. (1mk)

2. Complete the statement that follows.

Dimitri Mendeleev attempted to classify elements. He arranged elements in order of their ____________ . In the modern Periodic Table; elements are arranged in order of their ____________. (2mks)

a. Use dot (.) and cross (x) diagram to show the bonding in carbon (II) oxide molecule (2mks)

b. Label the type of bonds present. (1mk)

c. Carbon (II) oxide is a poisonous pollutant.

i. State how the gas gets into the air. (1mk)

ii. Explain its poisonous nature. (2mks)

4. Magnesium belongs to group (II) and period three of the periodic table.

i. State the other name for group (II) elements. (1mk)

ii. Write the electronic arrangement for an ion of magnesium. (1mk)

iii. Write an equation to illustrate the process occuring when the second ionization energy of magnesium is measured. (1mk)

iv. The neon atom and the magnesium ion have same number of electrons. They are said to be isoelectronic. Give two reasons why the first ionization energy of neon is lower than the third ionization energy of magnesium. (2mks)

5. Magnesium burns in the air to form Magnesium oxide where Magnesium ions and oxide ions are formed.

i. Draw a dot (.) energy level diagram to show the electronic structure of Magnesium ion. (Atomic number magnesium=12) (2mks)

Oxide ion (atomic number of oxygen=8) (2mks)

ii. Write a balanced equation for the above reaction. (1mk)

iii. Magnesium oxide dissolves slightly in water. State and explain the effect of the resulting solution to litmus paper. (2mks)

iv. Write a balanced equation for the reaction described in (iii) above. (1mk)

6. A metal W (not its actual chemical symbol) is found below magnesium in the same group of the Periodic Table.

i. Compare and explain their melting points. (2mks)

ii. In terms of electrons, state the meaning of the following terms. (2mks)
- Oxidation
- Oxidizing agent.

8. In the Periodic table between the main group (II) and group (III) is a block of elements with variable oxidation numbers, and colored compounds among other properties.

i. State the name given to this block of elements. (1mk)

ii. State two common elements that belong to this block of elements. (2mks)

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