COAS Chemistry 2 Teacher Resources Original Material Cambridge University Press 2005, 2007 s1

4 Marking scheme: End-of-chapter test

1 a [1]

[2] lone pair on oxygen [1] dipoles on oxygen and hydrogen [1] two hydrogen bonds [1] – + c CH3COOH(aq)  CH3COO (aq) + H (aq) reactant [1] products [1] state symbols are essential for both marks; if omitted then give just 1 mark or – + CH3COOH(aq) + H2O(l)  CH3COO (aq) + H3O (aq) reactant [1] products [1] state symbols are essential for both marks; if omitted then give just 1 mark

2 a i Carbon Hydrogen Oxygen Mass of element 54.5 g 9.1 g 36.4 g Number of moles 54.5 9.1 36.4 = 4.54 = 9.1 = 2.28 [1] 12.0 1.0 16.0 Relative number of atoms 4.54 9.1 2.28 = 2 = 4 = 1 [1] 2.28 2.28 2.28

empirical formula = C2H4O [1] ii the molecular-ion peak is at m/e = 88 [1] so relative molecular mass = 88 [1] relative molecular mass = 2  empirical formula mass [1]

the molecular formula = 2  empirical formula = C4H8O2 [1]

b CH3CH2CH2COOH [1]

[1]

CH3CH(CH3)COOH [1]

[1]

COAS Chemistry 2 Teacher Resources Original material © Cambridge University Press 2005, 2007, 2009 1 c i CH3CH2CH2COOH + C2H5OH  CH3CH2CH2COOC2H5 + H2O [1]

CH3CH(CH3)COOH + C2H5OH  CH3CH(CH3)COOC2H5 + H2O [1] – + ii 2CH3CH2CH2COOH + 2Na  2CH3CH2CH2COO Na + H2 [1] – + 2CH3CH(CH3)COOH + 2Na  2CH3CH(CH3)COO Na + H2 [1] – + iii 2CH3CH2CH2COOH + Na2CO3  2CH3CH2CH2COO Na + H2O + CO2 [1] – + CH3CH(CH3)COOH + Na2CO3  CH3CH(CH3)COO Na + H2O + CO2 [1] – + iv CH3CH2CH2COOH + NaOH  CH3CH2CH2COO Na + H2O [1] – + CH3CH(CH3)COOH + NaOH  CH3CH(CH3)COO Na + H2O [1] 3 a ethyl methanoate [1]

HCOOCH2CH3 [1]

[1]

methyl ethanoate [1]

CH3COOCH3 [1]

[1]

b i CH3COOCH3 + H2O  CH3COOH + CH3OH [1]

HCOOCH2CH3 + H2O  HCOOH + CH3CH2OH [1] – + ii CH3COOCH3 + NaOH  CH3COO Na + CH3OH [1] – + HCOOCH2CH3 + NaOH  HCOO Na + CH3CH2OH [1] c perfumes [1] flavourings in foods [1] solvents [1] 4 a i hexadecanoic acid [1] C16,0 [1] ii hexadec-9-enoic acid [1] C16,1(9) [1] iii octadec-5,9,13-trienoic acid [1] C18,3(5,9,13) [1] iv octadec-9,13-dienoic acid [1] C18,2(9,13) [1] b trans fatty acids are associated with the formation of ‘bad’ cholesterol; [1] this forms fatty deposits (atherosclerotic plaque) in arteries leading to heart disease, strokes etc. [1] c Formed by the combination of the alcohol/propan-1,2,3-triol (glycerol) [1] with three carboxylic (fatty) acids. [1] d biodiesel [1]