(a)(i) List the three types of particles present in atoms. (ii) name the element which does not contain all the three particles in its atom. Mention the particle that is not present.
(b) Give the reason why: (i) the relative atomic masses of some elements are not whole number; (ii) relative atomic masses are used instead of the actual masses of atoms in grams; (iii) metals are good conductors of electricity.
(c)(i) Name the type of bond present in the oxonium ion, (ii) State one effect of the existence of intermolecular hydrogen bonding on the physical properties of ethanol. (d)(i) Explain what is meant by water of crystallization. (ii) When 5.0g of a compound Y was heated to constant mass, 1.8g of water vapour was given off. Determine the number of molecules of water of crystallization in one molecule of Y, given that the molar mass of its anhydrous form is 160g. [H = 1, 0 = 16]
Explanation
(a)(i) The three types of particles present in atoms are proton, electron and neutron (ii) Hydrogen. Neutron is not present
(b)(i) Because of the existence of isotopes which we present in the same proportions. (ii) The actual mass is too small to be determined practically, hence the ratios of the masses of the atom to that of carbon —12 atom area used. (iii) Metals have a cloud of free a mobile delocalized valence electrons
(c)(i) Covalent bond and co-ordinate/dative covalent bond Boiling point is higher than expected or usually high. It is soluble in polar solvents/water.
(d)(i) Water of crystallization is a term used for describing the molecule of water which becomes loosely bound to the molecules of some salts on crystallizing. (ii) 5.0g of Y contains (5.0 - 1.8)g i.e 3.2g of anhydrous sari Molar mass of water = (2 x 1) + 16 = 18g No. of mole of anhydrous : No. of mole of water Salt \(\frac{3.2}{160}\) : nH\(_2\)O 0.02 : 0.1 \(\frac{0.02}{0.02}\) : \(\frac{0.1}{0.02}\) So, ratio = 1 : 5
There are 5 molecules of water of water of crystallization
