NYGH 2014-S3EOY-Chem P1 & P2 Ans

1 2014 Secondary Three End-of-Year Examination (Chemistry) Paper 1 1 D 6 B 11 C 16 A 21 A 26 D 2 B 7 A 12 A 17 A 22 B 27 B 3 B 8 C 13 C 18 C 23 A 28 B 4 C 9 B 14 C 19 C 24 B 29 D 5 B 10 D 15 B 20 D 25 A 30 C Paper 2 Section A No Answers Marks A1(a) Hexane and Heptane are miscible [1]. They have different boiling points that are close to each other/ less than 25oC [1]. [2] (b) temperature/oC 100 90 80 70 total volume of distillate axes – 1m graph – 1 m [2] A2 (a) XO2 [1] (b) 32 32 162 162XO in oxygen of ncompositio Percentage 2 +=×+ ×= xx ( ) [1] 0.28 944.14533.0 32056.17533.0 3232533.0 [1] 533.032 32 = = =+ =+ =+ x x x x x Practise Error Carry Forw ard (E.C.F.) if the formula of the oxide from (a) is incorrect. Example: X4O : 56.1, X 2O : 7.00, X 3O2: 9.35, X 8O9: 53.3, X 2O4: 28.0, X 4O2: 7.00, X9O8: 12.5, X2O3: 21 [1] A3(a)(i) Reaction 1: CaCO3 → CaO + CO2 [1] Reaction 2: CaO + H2O → Ca(OH)2 [1] [2] (a)(ii) Lime is used in agriculture to reduce the acidity of the soil so as to obtain appropriate pH for growth of plants./neutralise/ increase the pH of the soil. [1] (a)(iii) Sodium hydroxide is a stronger alkali which ionises completely to give a higher concentration of OH-. [1]

2 No Answers Marks (b)(i) CaMg(CO3)2 + 4HCl → CaMgCl4 + 2CO2 + 2H2O Accept this answer : CaMg(CO3)2 + 4HCl → MgCl2 + CaCl2 + H2O + 2CO2 [1] (b)(ii) mol 01023.0 21612 450.0CO of moles of No. 2 = ×+= ( ) .CO of mole 2 forms COCaMg of mole 1 equation, the From 223 ( ) [1] mol 0.005115 2 01023.0COCaMg of moles of No. 23 = = ( ) ( )[ ] g 94116.0 1631222440005115.0COCaMg of Mass 23 = ×+×++×= [1] %1.94 %100000.1 94116.0Purity Percentage = ×= Practise Error Carry Forward (E.C.F.) if the equation from (b)(i) is not balanced. [2] A4(a) J: van der waals forces / intermolecular forces of attraction. (intermolecular forces and hydrogen bond is not accepted. ) [1] (b) Greater energy is required to overcome the strong ionic bonds/electrostatic forces of attraction between oppositely charged ions [1] in K than the weak van der waals forces between molecules of J [1]. [2] (c) A large amount of energy [1] is required to overcome the strong electrostatic forces of attraction between the positive ions and the delocalised electrons/ overcome the strong metallic bond. [1] [2] A5(a)(i) sulfuric acid chemical formula is not accepted. [1] (a)(ii) Reaction of aqueous sodium hydroxide and sulfuric acid will yield sodium sulfate and water according to the equation 2NaOH(aq) + H2SO4(aq) → Na2SO4(aq) + H2O(l) [1] With the use of 0.100 mol/dm3 of NaOH, half the volume H2SO4 with the same concentration must be reacted with it to form Na 2SO4. /Titrate fixed volume of NaOH with H2SO4. [1] The salt solution is then heated until a saturated solution is formed and crystallised [1]. The crystals are dried by pressing between pieces of filter paper [1]. [4] (b) White precipitates are formed. [