Which of the following constitutes an advantage in the use of hard water?

• A. Formation of scum with soap
• B. Furring of kettles
• C. Blockage of water pipes
• D. Formation of strong bones

(a)(i) Arrange the following elements in the order of increasing reactivity. Iron, Lead, Magnessium, Aluminium.

(ii) Which of the following elements in (a)(i) above reacts with sodium hydroxide to give hydrogen?

(b) What property of tetraoxosulphate (VI) acid does each of the following reactions illustrate?

(I) S + 2H\(_2\)SO\(_4\) ---> 3SO\(_4\) + 2H\(_2\)O

(ii) MgO + H\(_2\)SO\(_4\) ---> MgSO\(_4\) + H\(_2\)O

(iii) C\(_{12}\)H\(_{22}\)C\(_{11}\) + H\(_2\)SO\(_4\) ---> 12C + H\(_2\)SO\(_4\) + 11H\(_2\)O

Student X titrated 25 cm³ of Na₂CO₃ with 0.1 mol dm?³ HCI, using methyl orange as indicator. Student Y carried out the same exercise but used phenolphthalein as an indicator. Which of the following statements about the titration is true?

• A. hydrogen chloride gas was released in the reactions in both titrations
• B. the titer values obtained from the titration are equal
• C. the tirer value obtained by X is twice that of Y
• D. the titer value obtained by Y is twice that of X

Two metallic ions commonly present in hard water are

• A. Ca²⁺ and Zn²⁺
• B. Cu²⁺ and Na⁺
• C. Mg²⁺ and Ca²⁺
• D. Fe²⁺ and Na⁺

When a solid melts and consequently boils, there is

• A. a gradual increase in the average kinetic energy of the particles
• B. a sudden decrease in the kinetic energy of the particles
• C. no change in the average kinetic energy of the particles
• D. a rapid change in the nature of bonding of the components

Electrons always occupy the lowest empty energy level is a statement of

• A. Aufbau Principle
• B. Hund's rule
• C. Pauli Exclusion Principle
• D. Periodic law

What is the amount (in mole) of hydrogen gas that would be produced if 0.6 mole of hydrochloric acid reacted with excess zinc according to the following equation? Zn(s) + 2HCI(aq) → ZnCI₂(aq) + H₂(g)

• A. 0.1 mole
• B. 0.2mole
• C. 0.3 mole
• D. 1.0 mole

A mixture of Nitrogen, Oxygen and Helium contains 0.25, 0.15 and 0.4 mole of these gases respectively. If the pressure contribution due to oxygen was 2.5atm. The partial pressure of Helium is

• A) 4.0 atm
• B) 0.8 atm
• C) 3.33 atm
• D) 6.67 atm

When cathode rays are deflected onto the electrode of an electrometer, the instrument becomes

• A. negatively charged
• B. positvely charged
• C. neutral
• D. bipolar

The gas obtained as a product of anaerobic action on organic matter buried in the earth is

• A. ethene
• B. methane
• C. carbon (IV) oxide
• D. nitrogen (IV) oxide