Explanation

Postulates of the kinetic theory of gases (any two)

(a)(i) Molecules move randomly in straight lines or molecules are in constant motion.

(ii) Molecules collide with one another and with the walls of container, the collision of the molecules are elastic.

(iii) The temperature of the gas is a measure of the average kinetic energy of its particle i.e the kinetic energy of the particles is proportional to the temperature of the gas.

(iv) Volume of the gas particle is negligible compared to the volume of the container.

(v) The attraction or repulsion of the gas particles is negligible.

(b) Chemical properties common to SO\(_2\) and CO\(_2\).

(i) They react with bases to form salts.

(ii) They turn lime water milky or the milkiness disappears with excess gas

(iii) They are acid anhydrides and turn moist or damp litmus paper red.

Explanation

(a)(i) Quantum numbers assigned to an electron in an atom are

9(i) n - (principal) quantum number

(ii) L - (azimuthal) sub principal quantum number

(iii) m - (magnetic quantum number) and (iv) s - (spin quantum number)

(ii) The maximum number of electrons that can occupy the 3d orbital is 10.

(b) The element p represented by the electronic configuration 1s\(^2\)s\(^2\)2p\(^6\)3s\(^2\)

(i) The electronic configuration of its ions is 1s\(^2\)2s\(^2\)2p\(^6\) Most likely formula of the chloride of P is PCl\(^2\)

(iii) P is a good reducing agent. Reducing agents are electron donors OR P would readily lose 2(two) electrons to form noble gas structure.

(c)(i) Electron affinity is defined as the energy evolved or liberated when 1 mole of an element in form of gaseous atoms form negative ions OR The energy liberated or absorbed when one mole of electron is added to an element in form of gaseous atoms.

(ii) Ammonia can participate in dative bonding because dative bonding involves the sharing of an electron pair donated by one atom. The nitrogen in ammonia has a lone pair of electrons which can be donated for sharing.

(d)(i) if an element in group IV loses an alpha particle, the product would belong to group II.

(ii) Since both X and Y are equally toxic, Y constitutes a greater health hazard than X which has a shorter half life because half life is the time taken to decay to half the initial value remains for a longer period in the body and being toxic causes damage for a longer period.

Explanation

(a) In increasing order of reactivity

(i) Lead < Iron < Aluminium < Magnesium OR Magnesium > Aluminium > Iron > Lead.

(ii) Give H\(_2\) with NaOH, Aluminium and lead

(b) H\(_2\)SO\(_4\) behaves as

(i) oxidising agent in reaction with S

(ii) typical acid (neutralisation) in reaction with MgO

(iii) dehydrating agent in reacticn with Cl\(_2\)H\(_{22}\)O\(_{11}\).

Explanation

(a) Uses of Na\(_2\)CO\(_3\)

- As a water softener

- For standardizing acids or as analytical reagent

- In the manufacture of glass. NaOH, paper, soap or detergent etc.

(b)(i) Hydrolysis accounts for the alkalinity of Na\(_2\)CO\(_3\)\(_{(aq)}\)

(ii) Sodium hydrogen trioxocarbonate (IV) is obtained when

- CO\(_2\) is bubbled into Na\(_2\)CO\(_{3(aq)}\).

Correct Answer: C. Dilute sodium chloride solution

Explanation

(a) IUPAC name of Fe\(_2\)(SO\(_4\))\(_3\) is iron (iii) tetraoxosulphate (VI)

(b)(i) Equation of reaction of H\(_2\)S and FeC\(_3\) is 2FeCI\(_3\) + H\(_2\)S \(\to\) 2FeCl\(_2\) + 2HCI + S.

(ii) Changes observed. Brown solution changes to green and yellow deposit is formed.

Correct Answer: D. CuO

Explanation

(a)(i) Definition: Activation energy. Activation energy is the minimum energy which reactant particles (reaction complex or reacting particles) must possess before a reaction can occur.

(ii) A Catalyst: It lowers or alters the activation energy or provides an alternative pathway with a lower activation energy.

(b)(i) (finely divided) nickel (platinum, paladium), catalyses the hydrogenation of oils.

(ii) Enzymes catalyse biochemical reactions.

Correct Answer: A. disinfectant

Explanation

(a)(i) Heat of neutralization is defined as the amount of heat evolved when one mole of hydrogen ions (H\(^+\)/H\(^3\)O\(+\)) from an acid reacts with one mole of hydroxide ions (OH\(^-\)) from an alkali to form one mole of water.

(ii) Neutralization can be used to prepare only soluble salts, hence CuCl\(_2\) which is soluble can be prepared by this method while PbC\(_2\) which is insoluble cannot.

(b)(i) Manufacture of HNO\(_3\) in outline by the catalytic oxidation of NH\(_3\). Ammonia reacts with air or oxygen in the presence of platinum-rhodium catalyst and a high temperature (of about 550 - 850°C) to form Nitrogen (11) oxide and steam. 4NH\(_3\) + 5O\(_3\) ---> 4NO + 6H\(_2\)O. Nitrogen (II) oxide reacts with more or excess air to give nitrogen (IV) oxide which is dissolved' in hot water in the presence of more air to give trioxonitrate (V) acid.

2NO + O\(_2\) —> 2NO\(_2\); 4NO\(_2\) + 2H\(_2\)O + O\(_2\) —> 4HNO\(_3\)

(ii) Oxygen, NaNO\(_3\) are obtained when NaNO\(_3\) is heated strongly.

(c) Reactions of Mg with nitrogen.

(i) Equations of the reaction 3Mg + N\(_2\) --> Mg\(_3\)N\(_2\).

(ii) Calculation of the amount of Mg\(_3\)N\(_2\) that can be obtained from 3.0g of Mg. From the equation, (3 x 24)g of Mg gives 1 mole of Mg\(_3\)N\(_2\).

3g of Mg will give 3 x \(\frac{1}{3 \times 24}\) mole of Mg\(_3\)N\(_2\) = 0.0417 mole.