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School of Chemistry & Physics, University of KwaZulu-Natal, Westville Campus, Durban General Principles of Chemistry – CHEM110 Tutorial 2 – 27 February & 1 March 2013 1. Chlorine has two naturally occurring isotopes 35Cl with an atomic mass of 34.968 u and a natural abundance of 75.53%, and 37Cl with atomic masses of 36.956 u and a natural abundance of 24.47%. Calculate the average atomic mass of chlorine. AM = ( % Cl-35 x IMCl-35 100 ) AM = ( 75.53 x 34.968 100 ) + AM = ( 2641 100 904.3 100 ) + ( ( + AM % Cl-37 x IMCl-37 100 24.47 x 36.956 100 ( ) ) ) = 26.41 + 9.043 = 35.45 u 2. Write the chemical formula for each of the following compounds: a) potassium sulfate K2(SO4) b) magnesium sulfide MgS c) calcium phosphate Ca3(PO4)2 d) silver perchlorate AgClO4 e) iron(III) dichromate Fe2(Cr2O7)3 f) tetraphosphorus heptoxide g) copper(II) cyanide h) potassium hydrogen phosphate K2HPO4 i) diammonium hydrogen phosphate (NH4)2HPO4 j) cobalt(I) chloride P4O7 Cu(CN)2 CoCl 3. Name each of the following compounds, and classify it as ionic or molecular: (a) PbO (f) Cr2O3 (b) CuS (g) Cl2O9 (c) P3O6 (h) Fe2(SO4)3 (d) K2CrO4 (e) RbCN (i) ICl5 (a) lead oxide, I (b) copper(II) sulfide, I (c) triphosphorus hexoxide, M (d) potassium chromate, I (e) rubidium cyanide, I (f) chromium(III) oxide, I (g) dichlorine nonoxide, M (h) iron(III) sulfate, I (i) iodine pentachloride,M 4.1 Balance the following equations: (a) 2H3PO4 + 3Mg(OH)2 → Mg3(PO4)2 + 6H2O (b) BaCO3 + 2HCl → H2O + CO2 + BaCl2 4.2 Aluminium oxide,Al2O3 , reacts with water to give Al(OH)3. Write a balanced equation for this process. Al2O3(s) + 3H2O(l) → 2Al(OH)3(s) 5. Which of the following reactions represents a (i) combination reaction, (ii) a decomposition reaction, (iii) a displacement reaction or (iv) combustion reaction? (a) (b) (c) (c) 2Na(s) + 2H2O(ℓ) → 2NaOH(aq) + H2(g) displacement rxn 2H2O + electric current → 2H2(g) + O2(g) decomposition rxn 2SrO(s) + CO2(g) → SrCO3(g) combination rxn C3H8(g) + 5O2 → 3CO2(g) + 4H2O(g) combustion rxn