2020 TJC Answers Promo

©TJC 2020 TJC Promo H2 Chemistry MCQ Worked Solutions 1 Answer: B Since J has a larger angle of deflection than 16O2–, it would have a greater charge/mass ratio than 16O2–. 2 Answer: C P+ : 1s2 2s2 2p6 3s2 3p2 Cu3+: 1s2 2s2 2p6 3s2 3p6 3d8 Ca: 1s2 2s2 2p6 3s2 3p6 4s2 S: 1s2 2s2 2p6 3s2 3p4 3 Answer: A No. of moles of ethanol molecules = 23 24+16+6 = 0.500 mol No. of moles of atoms in g of ammonia = 2.125 17 x 4 = 0.500 mol No. of moles of molecules in 11.35 dm3 of sulfur dioxide = 11.35 22.7 = 0.500 mol No. of moles of sodium ions = 250 1000 x 2 x 2 = 1.00 mol 4 Answer: B V C H O % 19.21 45.3 5.29 30.2 Ar 50.9 12 1 16 Amt 0.377 3.77 5.29 1.88 rati o 1 10 14 5 Empirical formula = VC10H14O5 Z = (5 – 1)/2 = 2 5 Answer: A H2S → S + 2H+ + 2e SO2 + 4H+ + 4e → S + 2H2O Reacting ratio: 2H2S Ξ SO2 6 Answer: D Bond angle 1 is around a sp 2 carbon atom with 3 bp, 0 lp = 120 Bond angle 2 is around a sp 3 carbon atom with 4 bp, 0 lp = 109.5 Bond angle 3 is around a N -atom with 3 bp, 1 lp = 107 7 Answer: C There are no hydrogen bonds existing between methanal molecules. Methanal is a polar hence pd-pd interactions exist between methanol which is stronger than id -id interactions between non polar ethane molecules. 8 Answer: A Hr= 4(–241.8) – 2(50.6) – (9.2) = –1077.6 kJ mol–1 9 Answer: D  2: Combustion reactions are exothermic in nature.  4: The stoichiometric ratio of sodium oxide is defined as 1 and sodium oxide is formed from its elements. 10 Answer: B Heat absorbed by water = 80.2  100 80 = 64.16 kJ = 64 160 J Heat absorbed by water = mcΔT 64 160 = m (4.18)(80 – 25) Mass of water = 279 g 11 Answer: D Since Kc remains constant, there is no change in position of equilibrium when temperature changes and the enthalpy change, H is zero.

©TJC 12 Answer: B Kc = [NH3]2[H2SO4] = 2.57 x 10-5 (2x)2(x) = 2.57 x 10-5 hence x = 0.0186 13 Answer: B  1 Vol of O2 (product) increases from 0 to 50cm3 (½ of max vol) in 20 s Vol of O2 (product) increases from 50 to 75cm3 (½ of maxi vol to ¾ of max vol) in 20 s half-life is a constant at 20 s.  2 Since half-life is a constant at 20s, the reaction is first order w.r.t. [H2O2]. 14 Answer: C Both kf and kb will increase while Kc remains constant as Kc is only temperature dependent. 15 Answer: A When p increases 5 2 times, the V should decrease 5 2 times to 38.4 cm3 if the gas is ideal. But V of the gas only decreases to 46 cm 3  Vreal > Videal 16 Answer: B (0.68)VT = (0.7)(1.0) + (0.5)(2.5) + (1.0)(1.5) VT = 5.074 dm3 Vol of connecting tube = 5.074 – (1.0 + 2.5 + 1.5) = 0.074 dm3 17 Answer: C An electrophile is an electron pair acceptor. They are positively or partial positively charged. They are attracted to electron rich sites or regions with high electron density. 18 Answer: A H radicals are not formed in free radical substitut