Mention the respective properties of the following allotropes of carbon that account for their uses as indicated:

(a) diamond used for drilling rocks;

(b) diamond used as jewels;

(c) graphite used as electrodes;

(d) graphite used for slowing down neutrons in nuclear reactors;

(e) wood charcoal used in gas masks.

What is the chemical structure of soap and detergent molecules?

• A. Hydrophilic head and hydrophobic tail
• B. Hydrophilic head and hydrophilic tail
• C. Hydrophobic head and hydrophobic tail
• D. Hydrophilic tail and hydrophobic head

Calcium and magnesium belong to the group of the periodic table because both?

• A. are metals
• B. form cations
• C. form colourless salts
• D. have same number of valence electrons

In solution, aminoethanoic acid (glycine) can be represented as NH₃3 CH₂COO. This implies that it

• A. is soluble in all inorganic liquids
• B. can function as a weak acid or a weak base
• C. does not form salt with mineral acids
• D. is highly acidic

Mg+ 2HCI(aq) → MgCI₂(g) + H₂(g) From the equation above what mass of hydrogen would be produced if 12.0 g of magnesium reacted completely with dilute hydrochloric acid? (H = 1, Mg = 24)

• D. 12.0g
• B. 2.0g
• C. 6.0g
• D. 12.0g

P(g) + Q(g) ↔ 3R(s) + S(g) ΔH is negative Which of the following will increase the yield of R?

• A. Using a larger close vessel
• B. Increasing the temperature
• C. Removing some S
• D. Adding a positive catalyst

If chlorine is bubbled into water and the resulting yellowish-green solution is exposed to bright sunlight for a while, the solution will decompose giving out

• A. oxygen and leaving behind aqueous hydrochloric acid
• B. chlorine and oxygen
• C. oxygen, hydrogen and chlorine
• D. oxygen, thereby producing hypochlorous acid

The energy required to remove an electron from the isolated gaseous atom is known as

• A) electron affinity
• B) bond energy
• C) lonisation energy
• D) electronegativity

Which of the following typically represents a photochemical reaction?

• A. Formation of water from hydrogen and oxygen molecules
• B. Conversion of dinitrogen (IV) oxide to nitrogen (IV) oxide
• C. Decomposition of calcium hydroxide to its oxide
• D. Conversion of silver halides to grey metallic silver

Which of the following gases will rekindle a brightly glowing splint?

• A. NO₂
• B. NO
• C. N₂O
• D. CI₂