How can contaminants be removed from water?

How many protons are there in a molecule of oxygen gas?

Match the elements in List A with the number of protons in List B by writing the correct response beside the corresponding item number in the table provided. List A List B () Hydrogen A Six Five (ii) Helium C Four (iii) Carbon D Ten (iv) Fluorine E Nine (v) Beryllium F Zero G Two Answers List A (i) (ii) (iii) (iv) (v) List B

1. Hydrogen (1 mk)
2. Helium (1 mk)
3. Carbon (1 mk)
4. Fluorine (1 mk)
5. Beryllium (1 mk)

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Describe the process of fractional distillation of a mixture of water and ethanol.

1. Describe the process of fractional distillation of a mixture of water and ethanol. (0 mk)

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Give two differences between covalent compounds and electrovalent compounds.

1. Give two differences between covalent compounds and electrovalent compounds. (0 mk)

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(viii) Which apparatus serves the function of stirring substances?

A sample of chlorine gas was found to contain 75% of the isotope 35Cl and 25% of isotope 37Cl. Calculate the relative atomic mass of chlorine.

1. A sample of chlorine gas was found to contain 75% of the isotope 35Cl and 25% of isotope 37Cl. Calculate the relative atomic mass of chlorine. (0 mk)
2. Write the nuclide notation of an arbitrary element X having atomic number Z and neutron number A. (0 mk)

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Identify the element which: (i) has the highest electronegativity. (ii) has a valency of four. (iii) is among the inert gases. (iv) belongs to alkaline earth metals' block. (v) burns in oxygen to form water.

1. Place the elements having proton number 1, 10, 14, 16 and 20 in the Periodic Table by using letters A, B, C, D and E respectively. (0 mk)
2. Identify the element which belongs to alkaline earth metals' block. (0 mk)
3. Identify the element which burns in oxygen to form water. (0 mk)

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Identify three fields in which Chemistry is applied.

1. Give three laboratory rules. (0 mk)
2. Identify three fields in which Chemistry is applied. (0 mk)

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(a) (i) Give three assumptions of Dalton's Atomic Theory. (ii) Write the nuclide notation of an arbitrary element X having atomic number Z and neutron number A. (b) A sample of chlorine gas was found to contain 75% of the isotope ³⁵Cl and 25% of isotope ³⁷Cl. Calculate the relative atomic mass of chlorine.

1. Give three assumptions of Dalton's Atomic Theory. (3 mk)
2. Write the nuclide notation of an arbitrary element X having atomic number Z and neutron number A. (1 mk)
3. A sample of chlorine gas was found to contain 75% of the isotope ³⁵Cl and 25% of isotope ³⁷Cl. Calculate the relative atomic mass of chlorine. (3 mk)

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What will be observed in the following simple experiments? (i) Red litmus paper is dipped into a flask containing dilute hydrochloric acid. (ii) A piece of white plain paper is placed above a luminous flame. (iii) A burning splint is lowered into a jar containing a mixture of hydrogen and oxygen gas.

1. Briefly explain three classes of fire by focusing on the nature of the burning materials and the recommended extinguishers. (0 mk)
2. If a person is surrounded by smoke to the extent of not being able to access the exits, it is advised to lie flat on the floor while searching for the exit points. (0 mk)
3. A burning splint is lowered into a jar containing a mixture of hydrogen and oxygen gas. (0 mk)

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SECTION C(15 Marks) Answer question ten (10). (a) Give four chemical properties of hydrogen gas. (i) (ii) (iii) (iv)

1. Give four chemical properties of hydrogen gas. (8 mk)
2. Draw a well labelled diagram of apparatus set up for the laboratory preparation of hydrogen gas. Include all chemicals involved. (7 mk)

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