RI 2023 A-Level H2 Chem Solution

This document is copyrighted, please do not reproduce it without permission © Raffles Institution 2023 A-Level H2 Chemistry Paper 1 Suggested Solutions 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 B C C D B D A C A A D D C C B 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 C C C A C A B A B D B D A B C Q1(B ) species proton no. no. of protons + neutrons no. of e– no. of neutrons Nd 60 145 60 145 – 60 = 85 Nd2+ 60 145 58 85 Pm 61 145 61 145 – 61 = 84 Pm3+ 61 145 58 84 Q2(C) The greater the difference in electronegativity between X/Y and C l/O, the greater the ionic character. compound difference in electronegativity XCl2 3.0 – 1.2 = 1.8 Y2O 3.5 – 0.9 = 2.6 XO 3.5 – 1.2 = 2.3 YCl 3.0 – 0.9 = 2.1 ZO2 3.5 – 1.8 = 1.7 ZCl4 3.0 – 1.8 = 1.2 Q3(C) A While C l is more electronegative than Br, causing CH 3Cl to be more polar and have stronger pd -pd interactions than CH 3Br, the significantly larger electron cloud side of Br causes the id- id interactions and hence the total IMF of CH 3Br to be stronger than that of CH3Cl. B There are no H -bonds between molecules of each compound. C Correct. Explanation in option A. D The relative boiling points is dependent on the IMF between the molecules and not the strength of the covalent bonds within the molecules. Q4(D) Shared electrons are circled. Q5(B) molecule structure polar? 1,1-difluoroethene Yes cis-1,2-difluoroethene Yes trans-1,2-difluoroethene No tetrafluoroethene No

This document is copyrighted, please do not reproduce it without permission © Raffles Institution Q6(D) Period 3 element Outermost shell Na Mg Al Si P S Cl Ar Elements with only 1 orbital i n outermost shell which contains just one electron = Na, Al & Cl Elements with only 1 orbital i n outermost shell which contains a pair of electrons = Mg, Al, Si & P Q7(A) 1 Correct. Down group 2, the E values become more negative i.e. the position of equilibrium lies more to the left, indicating that the group 2 elements are more readily oxidised and become stronger reducing agents. 2 Correct. Down group 2, the size of the 2+ cations increase, causing a decreasing in the charge density and polarizing power of the cations. The C –O bond of the carbonates are polarized to a lesser extent, requiring more energy to break, increasing the thermal stability of the metal carbonate. 3 Incorrect. See option 2. Q8(C) Let x be the percentage of 29Si in the sample. (92.23/100)(28) + (x/100)(29) + (0.0777–x)(30) = 28.10 x = 5.54. Q9(A) H2SO4 + 2NaOH → Na2SO4 + 2H2O Amt of H2SO4 = (50.0/1000)(2.00) = 0.100 mol Amt of NaOH = (100/1000)(1.00) = 0.100 mol NaOH is the limiting reagent. ⇒ No. of moles of water formed = 0.100 mol q = (100 + 50)(4.18)(29.0 – 20 .0) = 5643 J ∆𝐻𝐻 = − 5643 0.100 = −56.4 𝑘𝑘𝑘𝑘 𝑚𝑚𝑚𝑚𝑚𝑚−1 Q10(A) CaCl and CaCl2: Since Ca2+ has a higher charge and smalle