(a) Consider the following table; (i) Which of the elements:
| Element | Atomic Number | Mass Number |
| J | 9 | 19 |
| Q | 13 | 27 |
| R | 16 | 32 |
| X | 19 | 39 |
| Y | 24 | 52 |
I. is a halogen?
II. is most likely to be attracted by a magnet?
III. belongs to group I?
IV. would readily form an ion with a double negative charge?
(ii) What type of bond would exist between J and X when they combine?
(iii) How many neutrons are there in Q?
(iv) Write the formula of the compound formed when R combines with X.
(v) State the element which exists as diatomic molecule..
(vi) Select the element which belong to the d-block of the periodic table.
(b)(i) Explain briefly the term atomic orbital
(ii) I. State three prostulates of Dalton’s atomic theory.
II. List two limitations of this theory in the study of the atom
(iii) Describe briefly the structure of sodium chloride in its solid state.
(c) A sample of carbon is burnt at a rate of 0.50g per second for 30 minutes to generate heat.
(i) Write a balanced equation for the reaction
(ii) Determine the:
I. volume of carbon (IV) oxide produced at s.t.p.
II. moles of oxygen used up in the process at s.t.p. [C = 12.0, O = 16.0, Molar volume V\(_m\) = 22.4 dm\(^3\)].
Explanation
(a) Considering the following table.
| Element | Atomic Number | Mass Number |
| J | 9 | 19 |
| Q | 13 | 27 |
| R | 16 | 32 |
| X | 19 | 39 |
| Y | 24 | 52 |
(i) I. J is Halogen.
II. Y is most likely to be attracted by magnet.
III. X belongs to group I.
IV. R wduld readily form an ion with a double negative charge.
(ii) Type of bond that can exist between J and X when they combine: – Ionic/Electrovalent bond.
(iii) Neutrons in Q – 14
(iv) Compound formed when R combines with X: – X\(_2\)R.
(v) Element that exists as diatomic molecule: – Element J.
(vi) D-block element of the periodic table: Element Y.
(b)(i) Explain the term Atomic Orbital: This is a region/space within a principal energy level where there is high probability of finding an electron or an area where the electron lives.
(ii) I. Postulates of Dalton's atomic theory: –Matters are made up of small indivisible particles called atoms. –Atom can neither be destroyed nor created. –Atoms of the same element are identical but different from atoms of other elements. –Atoms combine (to form compounds) in simple whole number ratio.
II. Limitations of Dalton's Atomic Theory: –Atoms are divisible (protons neutrons and electrons). –Atoms can be created and destroyed (in nuclear reaction). –Existence of polymers (large) organic molecules. –Existence of isotopes.
(iii) Structure of sodium chloride in solid state: Soldium chloride (Nacl) as an ionic solid compound exists in crystal lattic/face centred cube which is made up of positive and negative ions.
(c) A sample of carbon is burnt at a rate of 0.50 g per second for 30 minutes to generate heat:
(i) Balance equation for the reaction: C\(_{(s)}\) + O\(_{2(g)}\) -> CO\(_{2(g)}\)
(ii) Determine the: I. Volume of carbon (IV) oxide produced at s.t.p. Mass of carbon burnt = 0.5 x 30 x 60 = 900 g from the reaction equation. 12 g of carbon at s.t.p produces 22.4 dm\(^3\) of CO\(_2\)
900 g of carbon = \(\frac{22.4}{12}\) x 900 = 1680 dm\(^3\)
II. Moles of oxygen used up in the process at s.t.p. from the reaction equation:
I mole of O\(^2\) used = 1 mol of CO\(_2\) produced.
But 22.4 of O\(_2\) = 1 mole of O\(_2\).
:. 1680 dm\(^3\) of O\(_2\) = \(\frac{1}{22.4}\) x 1680 = 75.0 mol
OR
Mol of O\(_2\) = \(\frac{900}{12}\) = 75.0 mol.