2022 DHS Y6 H2 Prelim Paper 1_Worked Solutions

2022 Y6 Preliminary Examination H2 Chemistry 9729 Paper 1 Suggested Solutions © DHS Chemistry Unit Page 1 of 7 Answer Key 1 2 3 4 5 6 7 8 9 10 B A A B D D C B C D 11 12 13 14 15 16 17* 18 19 20* D C C B A A A C D B 21 22 23* 24 25* 26* 27 28 29 30 D C D B A A C B C D 1 B Given: angle of deflection  q m +15○ = k( +1 1 ) k = +15 –5○ = +15( q m ) q m = – 1 3  A q = 0 m = 1+2 = 3  q m ≠ – 1 3  B q = +3−5 = −2 m = 3+3 = 6  q m = – 1 3  C q = +4−1 = +3 m = 4+5 = 9  q m ≠ – 1 3  D q = +4−3 = +1 m = 4+5 = 9  q m ≠ – 1 3 2 A Interpretation of the graph: C is likely to be in Group 1 since it has the lowest 1 st IE. Since the four elements are consecutive, B is in Group 18 and A is in Group 17. 3 A  1 O3 O O O Bond angle <120  2 PF5 Bond angles 90, 120  3 [PCl4]+ P Cl Cl Cl Cl Bond angle 109.5  4 SF6 Bond angle 90 4 B  A CH3 CH3 H H This hydrocarbon is a non-polar molecule  B CH3 CH3 O The C=O bond has a r elatively large dipole moment (due to the large difference in the electronegativities of carbon and oxygen ) and there are no other significantly polar bonds to offset the dipole moment of the C=O bond Thus, the molecule has the largest overall dipole moment among the four options.  C CH3 CH3 Cl Cl C-Cl bond is polar but the dipole moments cancel out.  D O Cl Cl C=O bond is more polar than C –Cl bond as O is more electronegative than C l but since both bonds are polar, there will be some degree of offset of dipole moments of the bonds, hence this molecule does not have the largest overall dipole moment among the four options. 5 D Both CO 2 and C l2 are non -polar molecules with weaker instantaneous dipole -induced dipole interactions (id-id) as compared to CH3OH and N2H4, which have stronger intermolecular hydrogen bonding. N 2H4 has more extensive hydrogen bonds (an average of 2 H-bonds per molecule) than CH3OH (an average of 1 H -bond per molecule), hence N 2H4 exhibit greatest deviation from ideal gas behaviour.

Dunman High School 2022 Y6 Preliminary Examination – H2 Chemistry 9729/01 Solutions © DHS Chemistry Unit Page 2 of 7 Per molecule CH3 O HCH3 N N H HH H Total no. of H atoms bonded to O/N atom(s) 1 4 No. of lone pairs on O/N atom(s) 2 2 Average no. of H bonds possible 1 2 6 D Possible identities of X: P4O10(s) + 6H2O(l) → 4H3PO4(aq) SO3(g) + H2O(l) → H2SO4(aq)  Possible identities of Y: Al2O3 is insoluble in water but is amphoteric, however one mole of Al2O3 requires 6 moles of H + for neutralisation, Al2O3(s) + 6H+(aq) → 2Al3+(aq) + 3H2O(l) hence, options A and B are incorrect as they do not match the required mole ratio stated in the question with both given options for X. Na2O(s) + H2O(l) → 2NaOH(aq)