2021 SASS 4E Chem MYE P2 Ans

1 CHEMISTRY 6092/2 Paper 2 80 Marks ______________________________________________________________________________________________________________________________________________________________________________________ MARKING SCHEME ______________________________________________________________________________________________________________________________________________________________________________________ SECTION A [50 Marks] Qn Answer Mark Remarks 1(a)(i) G 1 1(a)(ii) F 1 1(a)(iii) H 1 1(a)(iv) F 1 1(b) test tube 1 – D test tube 2 – G 1 1 2(a)(i) same element forming different structures / different forms of the same element 1 2(a)(ii) octasulfur larger relative molecular mass (Mr) for a larger intermolecular force of attraction, requiring more heat energy to overcome 1 1 Relation must be evident 2(b)(i) contains different number of neutrons 1 2(b)(ii) (0.9401 × 32.0) + (0.0076 × 33.0) + (0.0523 × 34.0) = 32.11 M1 A1 Rej. for wrong sig.fig. 2(b)(iii) difference in the abundance / %composition of isotopes 1 3(a)(i) B does not attain / have / acquire stable noble gas electronic configuration 1 Accept if mentioned of only 6 outershell e– instead of 8 for EC 3(a)(ii) gas simple covalent structure weak intermolecular forces of attraction present 1 1 1 Rej. explanations if incorrect physical state provided 3(b)(i) Mg atom does not share electrons with H Mg atom loses two valence electrons to form Mg2+ 1 1 Ignore any explanation wrt H 3(b)(ii) correct number of electrons for each ion correct charge annotated for each ion 1 1 3(b)(iii) free moving / mobile ions (Mg2+ & H–) as charge carriers that conduct electricity 1 Rej. electrons – ╳ ● H 4 © UCLES 2019 5070/12/M/J/19 6 A m i n e r a l d e p o s i t i s f o u n d t o c o n t a i n s m a l l grains made entirely of the element carbon. Which property will definitely be true of the grains of carbon? A T h e y w i l l b e m a d e o f a t o m s a r r a n g e d i n l a y e r s . B T h e y w i l l b e s o f t . C T h e y w i l l b u r n t o g i v e c a r b o n d i o x i d e . D T h e y w i l l c o n d u c t e l e c t r i c i t y . 7 W h i c h d i a g r a m s h o w s t h e o u t e r e l e c t r o n a r r a n g e m e n t i n c a l c i u m f l u o r i d e ? F FCa F– Ca2+ an electron from calcium an electron from fluorine key A B C D F– F– Ca2– F– F FCa 8 H o w m a n y s h a r e d p a i r s o f e l e c t r o n s a r e t h e r e i n o n e c a r b o n d i o x i d e m o l e c u l e ? A 2 B 4 C 8 D 1 2 2+ Mg 2 ST ANDREW’S SECONDARY SCHOOL MID-YEAR EXAMINATION 2021 SECONDARY 4 EXPRESS GD Updated: 07/05/2023

2 4(a) Cu2+ , Fe2+ , Fe3+ all give coloured solutions instead of colourless observed 1 4(b) Pb(NO3)2 either Pb2+ or Ag+ will result in ppt formed require half of the amount of T added for