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Question 1 of 8
1. Question
(a) (i) State three Bohr’s postulates of hydrogen atom. (1½ marks)
(ii) Calculate the wavelength (nm) of the spectral line of hydrogen atom for which n, = 3 and n2 = 6. (R = 1.09678 xl07m’) (2 marks)
(b) State the type of chemical bonds in each of the following:
(i) Na20 (ii) BeCl, (in) F3BNH3 (iv) C02 (v ) VNH (vi) NaCl (3 marks)
(c) The isotopic masses of two isotopes are 34.969 and 36.9689 amu respectively. Estimate the relative atomic mass of the element if the percentage abundance of the heavier isotope is 24.47%. (2 marks)
(d)(i) Write the electronic configuration of strontium 38Sr.
(ii) What block does it belong? (1½ marks)
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Question 2 of 8
2. Question
(a) (i) Define the term ionization energy. (1 mark)
(ii) State two factors that affect ionization energy of an atom. (1 mark)
(b) 500 mg of iron (II) complex ferrous bisglycinate hydrochloride was dissolved in dilute H2S04 and titrated with 0.0200 mol.dm”3 KMn04. 18.10 cm3 of KMn04 solution were required to reach the end point.
The equation for the titration reaction is as follows:
5Fe2++ MnO”4 + 8H+ —> 5Fe2++ Mn2++ 4H20
Calculate the
i. Number of moles of Fe+ in the capsule,
ii. Mass of iron in the capsule
iii. Molar mass of the iron (II) complex, assuming 1 mole of the complex contains 1 mole of iron. (Fe = 55.9 gmol-1) (3% marks)
(c) Identify each of the following reactions as precipitation, neutralization, decomposition or combination,
(i) Ba(OH)2(aq) 2HI(aq) —> Bal2(aq) 2H20(1)
(ii) Al(s) + 3Cl2(g) —> 2A1 Cl3(s)
(iii) Pd(N03)2(aq) + H2S(g) —> PdS(s) + 2HN03(aq)
(iv) Cu(N03)2(aq) —> CuO(s) + N02(g) + >/202(g)
(v) FeCl2(aq) + 2NaOH(aq) —> Fe(OH)2 (aq) + 2NaCl(aq) (2½ marks)
(d) The following results were obtained from a replicate analysis of blood sample for its Lead content: 0.752, 0.756, 0.752, 0.769 ppm Lead. Explain the precision of the results. (2 marks)
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Question 3 of 8
3. Question
(a) (i) State the two factors that affect the solubility of a solid in a liquid. (1 mark)
(ii) A saturated solution of AgCl was found to have a concentration of 1.3xl0″5mol/dm3. What is the solubility product of AgCl? (1½ marks)
(b) Define theiferms: (i) entropy and (ii) enthalpy. (2 marks)
(c) The equation for the reaction between sulphur trioxide and CuO is: CuO(s) + S03(g) —> CuS04(s)
Given the following data:
(i) Calculate the standard free energy for this reaction at 37°C.
(ii) Comment on the spontaneity of the reaction based on the value in (i). (3 marks)
(d) If the same volume of NH3 and an unknown gas X effuse at a rate of 2.25 cm3 s and 1.40 cmV1 respectively under the same experimental conditions, what is molecular mass (Mr) for X? Suggest a possible identity for X. [N = 14, H = 1.00] (2½ marks)
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Question 4 of 8
4. Question
(a) Calculate AH for the reaction; 4HI + 02 —> 2I2 + 2H20, given the following:
(i)H2 + I2 —> 2HI AH = +52kJ
(ii) 2H2 + 02 —> 2H,0 AH = -480 kJ (3 marks)
(b) Determine the equilibrium constant for the following reaction at 45°C
Sn2+(aq) + Cu2+(aq) Sn4+(aq) + Cu(s)
Given that:
Ee Cu27Cu = +0.337V
E° Sn47 Sn2+ = + 0.5V
R=’8.314Jmol’-1K-1 (31/2 marks)
(c) State-three (3) factors that affect the rate of a chemical reaction (1½ marks)
(d) Consider the reaction represented by the equation below:
CH3COOH(l) + C2H5OH (1) CH3COOC2H5(l) + H20(1)
Explain the effect on the position of the equilibrium on addition of:
(i) CH3COOC2H5(l)
(ii) C2H5OH (1) (2 marks)
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Question 5 of 8
5. Question
(a) (i) Define the term allotropy. (1 mark)
(ii) Name two alio tropes each of Carbon and Tin. (2 marks)
(iii) What is the difference between the type of allotropy exhibited by Carbon and Tin? (1 mark)
(b) Give reason(s) for the following observations: (3 marks)
(i) Fluorine exhibits only -1 oxidation state while other members of the group exhibit -1 as well as other oxidation states.
(ii) Hydrogen chloride is a stronger acid than hydrogen fluoride.
(iii) Beryllium does not react with water, even on heating
(c) Using suitable reaction equations, outline three (3) methods of laboratory syntheses of H2 from suitable metals. (1½ marks)
(d) State three (3) properties of transition elements. (1½ marks)
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Question 6 of 8
6. Question
(a) The molecular formulae of coordination compounds A and B are:
A = [Cr(NH3)4Cl2]Br B = [Cr(NH3)4(Br)(Cl)]Cl
(i) Give the IUPAC name of the compounds A and B. (2 marks)
(ii) State the oxidation number of the metal ion in both compounds. (1 mark)
(iii) Which of these compounds would give a white precipitate with silver nitrate solution? (1 marks)
(b) Using a statement and appropriate equation(s) where necessary, distinguish between synthesis gas and water gas. (2 marks)
(c) Using reaction equations only, show how Li, Na and K react when heated in excess Oxygen. (1½ marks)
(d) Describe, using chemical equations where applicable, how Aluminium is extracted from its ore. (3 marks)
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Question 7 of 8
7. Question
(a)(i) Define the term hybridization. (1 mark)
(ii) Indicate the hybridization of the Carbon atom labelled (a) – – (e) in the structure below:
(b) The scheme below represents the various reactions of propanone. Give the formula of each product represented by letters A to E
(c) Draw the structure of the following compounds. (3 marks)
(i) 2-bromo-3-chloro-4,4-dimethylpentanal.
(ii);Butane-l,2,3-triol.
(iii) 2,4,6-tribromophenol.
(d) A compound K, [C7H160] is an alcohol which is oxidized by Chromic acid to yield compound L [C7H140]. L forms crystalline 2,4- Dinitrophenylhydrazine compound and gives iodoform when treated with iodine-alkali but does not form a red precipitate with Fehling’s reagent. With the given data, write possible structures for compounds K and L. (1 mark)
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Question 8 of 8
8. Question
(a) (i) Define biotechnology (1 mark)
(ii) List two advantages in the use of biotechnology. (1 mark)
Explain the following terms:
(i) Inductive effect
(ii) Electromeric effect
(iii) homolytic cleavage. (1½ marks)
(c) Classify each of the following carbohydrates as Monosaccharides, Disaccharides, or Polysaccharides.
(I) Cellulose (II) Fructose (III) Glucose (IV) Maltose (V) Sucrose
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