EJC EJC 2020 GCE A Level 8873 H1 Chemistry Paper 2 (Suggested Solution)

EUNOIA JUNIOR COLLEGE

g 2Pb  Pb g e 32PbCO gas 14.43 207.2 212.0 316.0 14.43 327.2 0.04410 mol 2600 0.1083 mol24000 n n       3 2Pb CO :nn gas 0.04410:0.10831: 2.5 2:5 The molar ratio of Pb(CO3)2 to the gases follows the stoichiometry of equation 1. Hence lead(II) oxide is the final solid produced obtained.

Firstly, employ a lower reaction temperature . Equilibrium will shift to the right in attempt to counter this change by releasing heat energy (exothermic direction), thereby increasing the percentage yield. Secondly, increase the partial pressure of ethene in the reaction chamber. Equilibrium will shift to the right in attempt to remove the added ethene, while at the same time reacting with more steam, increasing the percentage yield. Lastly, decrease the volume of the reaction chamber. Equilibrium will shift to the right with fewer gaseous particles in attempt to decrease the total pressure, increasing the percentage yield    25 2 4 2 C H OH C HH O mol–1 dm3 Since the forward reaction is exothermic , increasing temperature will cause the position of equilibrium to shift left, to remove heat energy in attempt to lower the temperature. [C2H5OH] decreases while [C 2H4] and [H 2O] increases at equilibrium, hence lowering Kc. Firstly, when reaction temperature is lowered, fewer reactant molecules have sufficient energy to overcome the activation energy upon collision. In addition, the molecules move more slowly, lowering the number of collisions. Hence number of effective collision decreases, lowering the rate of reaction. The second and third change, increases the partial pressure of ethene and increases the total pressure, respectively. Both lead to an increase in the number of collisions between the molecules, hence increasing the number of effective collision and thus increasing the rate of reaction.

Solid potassium fluoride has a giant ionic lattice structure, comprising of oppositely charged K+ and Cl– ions, held together in a regular lattice by electrostatic attraction. Solid napthalene has a simple covalent (lattice) structure, comprising of discrete non-polar napthalene molecules held together in a regular lattice by instantaneous dipole-induced dipole attractions. Solid silicon dioxide has a giant covalent (lattice) structure, comprising of a regular covalent network of tetrahedrally bonded silicon and linearly bonded oxygen atoms held together by strong Si–O covalent bonds as shown below: Solid iron has a giant metallic (lattice) structure, comprising of an array of positively charged iron ions, held together in a regular lattice, by electrostatic attraction with a sea of delocalised electrons.

C14H18N2O5 carboxylic acid primary amine secondary amide ester 2 2 22RCO H 2Na 2RCO Na H 

CH3OH

LDPE has lower crystallinity and hence is softer and more flexibility compared to HDPE, allowing greater ease for coating the curved interior of a coffee cup. LDPE has significant branc