EJC 2021 GCE A-Level H1 Chemistry Paper 2 Suggested Solution

EUNOIA JUNIOR COLLEGE

A heterogeneous catalyst is a substance which is different in phase from the reactants, and increases the rate of a reaction by providing an alternative reaction pathway with lower activation energy, while remaining chemically unchanged at the end of the reaction. The large surface area to volume ratio of platinum nanoparticles. Inhaled nanopartciles can be deposited throughout the human respiratory system, followed by translocation potentially to the brain, liver and spleen. In view of the larger surface area, nanoparticles may show an increased toxicity compared to larger particles of the same chemical composition.

CO is oxidised to CO2 since the oxidation number of carbon increases from +2 in CO to +4 in CO2, while NO is reduced to N2 since the oxidation number of nitrogen decreases from +2 in NO to 0 in N2. Increasing the pressure causes the gas molecules to be closer together, therefore increasing the frequency of collision between the molecules. As a result, the frequency of effective collision also increases, leading to an increase in the rate of reaction.

    5.18410 mol 5.18410 mol  32 32 32 4 NaOH  34 CH CO HNaOH 343 CH CO H 3 CH CO H 16.200.03205.18410 mol 1000 in 25.0 cm of diluted vinegar  nn5.18410 mol 250 in 250 cm of diluted vinegar25.0 in 25.0 cm of sam n n n      32 3 CH CO H 3 3 32 ple in 250 cm of diluted vinegar 5.18410 mol CH CO H in original sample5.18410 mol 0.20736 25.0 n 3 1000 0.207 mol dm   13     3 32 3 CH CO H0.20736 mol dm 0.20736 mol212.041.0216.0 g mol dm 12.44 g dm Assuming a density of 1 g cm–3, this translates to 12.44 g of CH3CO2H in 1000 g of vinegar   12.44 g % by mass of ethanoic acid100% 1000 g1.24% Since the % by mass of ethanoic acid is below 5%, the vinegar would taste pleasant.

The end-point of a weak acid-strong base titration like in this case has a pH > 7. If the working range of the indicator is below that of the end-point pH and before the region of rapid pH increase, it will change colour before the end-point, leading to a smaller mean titre volume. A buffer solution is one that is capable of resisting pH changes when small amount of acid or base is added. When small amount of an acid is added, the equilibrium shifts to the left thereby removing the acid. When a small amount of a base is added, the base is removed by the H+, where the equilibrium shifts right to replenish the H+. Since small amount of acid and base is removed, the pH remains relatively constant.  X  n n 2 2 H XH r 0.912 0.0380 mol24.0 0.0380 mol 1.02 26.840.0380 n A Since X is divalent, it is likely to be magnesium.

Terylene has high tensile strength and ability to stretch and is less prone to creasing. This is because there is restriction rotation about the C=C and each of the double bond C has two different substitutents on it. The ester functional group in Terylene may undergo alkaline hydrolysis when treated with sodium hydroxide.

ethane-1,2-diol addition condensation polyamide

At any given pressure, the yield increases with temperature, meaning that the position of equilibrium lies more to the right (product side), favouring the forward reaction. Hence, the forward reaction is endothermic as the system attempts to counter the increase in temperature by absorbing heat. At any given temperature, the yield increases with pressure, meaning that the position of equilibrium lies more to the right, favouring the forward reaction. Hence, the forward reaction involves a decrease in the total number of molecules as the system attempts to counter the increase in pressure by reducing the number of gaseous molecules. When temperature increases, the proportion of molecules with energy more than or equal to the activation energy increases. Also, the average kinetic energy of the molecules increases, increasing the frequency of collision. Both leads to an increase in the frequency of effective collsion and hence the rate of reaction.

Increasing the temperature increases the rate constant for a reaction since the proportion of molecules with energy greater or equal to the activation energy increases. H = +210 kJ CH4 + 2H2O CO2 + 4H2 CO + 3H2 + H2O H = –42 kJ

diamagnetic paramagnetic paramagnetic 2s2 2p6 3s2 3p6 2s2 2p4 2s2 2p6 3s2 3p6 3d6 4s2