a) A-Non-metal, B-Metal, D-Metal, E-Non-metal
b) i. C
c) Noble gas usually don’t have oxidation states as their atoms have a stable electronic configuration, fully filled shells and thus they do not need to gain or lose electrons.
a) i. the more reactive the metal, the higher temperature needed for reduction
iron is more reactive than lead but less reactive than zinc, thus temperature to reduce iron oxide is higher than 400 and below 900⁰C.
b) magnesium and silver oxide
c) zinc oxide and hydrogen
Petroleum ; cracking
b) i. both reactions are neutralisation. Both reactions form same products which are water and salt.
ii. Hydrochloric acid is a strong acid that ionises completely in water to form hydrogen ions. Ethanoic acid is a weak acid that ionises partially in water to form hydrogen ions. Thus concentration of hydrogen ions is higher in hydrochloric acid than ethanoic acid.
b) Extraction from bauxite involves dissolving in ionic solvent at 900⁰C which is at higher temperature and requires higher amount of heat energy than heating aluminium can pieces to 700⁰C. Extraction from bauxite also involves electrolysis which requires very large amount of energy.
c) Carbon dioxide is a greenhouse gas that speeds up global warming, causing polar ice caps to melt faster and low lands to flood.
Concentrated sodium hydroxide is very corrosive and can cause burns to animals, kill aquatic lives and plants.
d) Aluminium is a finite resource and recycling enable resources of aluminium to last longer.
e) i. alloy
ii. harder, , the atoms are of different sizes of different elements in duralumin. This disrupts the regular arrangement of the pure aluminium. It is harder for the layers of atoms to slide over each other.
a) Cathode: 2H+ (aq) + 2e- → H2 (g)
Anode: 4OH- (aq) →2H2O (l) + O2 (g) +4e-
b) i. 1 mole of hydrogen gas formed only involves 2 mole of electrons but 1 mole of oxygen gas involves 4 moles of electrons which is twice the number of moles of electrons required by hydrogen gas.
ii. oxygen is very slightly soluble in water, causing the ratio of hydrogen to oxygen to be great than 2:1
iii. as electrolysis proceeds, there is lesser volume of water and more oxygen dissolved. When water left become saturated with dissolved oxygen, oxygen stops dissolving in the remaining solution.
c) Concentration increases, volume of water decreases.as more water molecules are broken down to form hydrogen and oxygen, there is lesser moles of water left with same moles of sodium chloride,
d) Similarity: hydrogen produced at cathodes
Difference: electrolysis of concentrated sodium chloride solution produces chlorine at anode but of dilute sodium chloride solution produces oxygen and water.
e) It is inert and do not interfere with the reactions occurring at electrode, it just connects the electrical circuit and the solution.
a) It is less reactive than quicklime and slakedlime thus it needs to be ground to very fine powder, very large surface area in order to react with acids.
b) i. there are other non-metal compounds that can be a source of nutrients for the plants to absorb.
c) ii. group IV and V oxides are usually non-metal oxides and form acidic oxides. Acidic oxides cannot react and neutralises acids.
d) % of Ca in CaO = 71.4%
% of Ca in CaCO3 = 40.0%
% of Ca in Ca(OH)2 = 54.0%
e) 6 X 106 dm3
a) The more carbon atoms in the alkane molecule, the higher melting or boiling point of the alkane
b) Propane. Its melting point should be above ethane as it has one more carbon atom, but its melting point is lower than of ethane instead.
c) -72⁰C; 100⁰C
d) As the number of carbon atoms increase from 2 in ethane to 6 in octane, the boiling point of alkane increases from -89 to 126⁰C and the flashpoints also increases from -104 to 13⁰C.
e) The more branched the isomer, the lower temperature of the flashpoint. Flashpoint of Straight chain pentane is at -49⁰C, and decreases to -57⁰C in branched alkane 1 with a branch and to -65⁰C with two branches. This is due to the more branched alkane molecule has smaller size and lesser surface area which leads to less extensive intermolecular forces between the molecules, less energy is needed to overcome these forces and burn more easily.
f) i. In winter, temperature is much lower. The mixture contains pentane and branched alkane 2 which has much lower flashpoint points and evaporates, burns more easily, releasing heat energy at a fast rate. This also helps to release enough energy to ignite octane.
ii. in hot weather, temperature is much higher. Molecules in petrol blend will boil due to low boiling points and vaporise easily and diffuse out of tank.
a) the amount of carbon monoxide will decrease as there is more air, more oxygen for complete combustion of the fuel to take place producing more carbon dioxide and less carbon monoxide as there is lesser incomplete combustion taking place. The amount of nitrogen monoxide will decrease as the running temperature of the engine is lower. Lesser heat energy is available to break the triple bond in nitrogen molecules to react with oxygen to form nitrogen monoxide.
b) 2CO + 2NO → 2CO2 + N2
c) i. increased amount of air provides more oxygen for oxidation of carbon monoxide to carbon dioxide, thus the percentage of carbon monoxide removed successfully increases as oxygen is the limiting reactant. The percentage of carbon monoxide removed successfully remained high and constant as oxygen is no longer the limiting reactant. The percentage of nitrogen monoxide removed successfully Initally was high and remained constant as there was very little oxygen available. When the amount of air in pollutant gases increases, there is more oxygen provided to oxidise nitrogen back to nitrogen monoxide. Thus the amount of nitrogen monoxide increases.
ii. percentage of carbon monoxide and nitrogen monoxide successfully removed depends on the amount of air in the pollutant gases, this shows that carbon monoxide and nitrogen also reacts with oxygen other than with each other.
a) When lithium chloride dissolves in water, the energy change is exothermic when sodium chloride dissolves in water, the energy change is endothermic. the magnitude of energy change is greater in dissolving lithium chloride than sodium chloride. Lithium chloride dissolving in water will cause temperature of surroundings to increase, temperature change is positive but sodium chloride dissolving in water will cause temperature of surroundings to decrease, temperature change is negative. The magnitude of temperature change is greater in dissolving lithium chloride than sodium chloride.
b) i. it is an endothermic process, indicating less heat energy is released into the water than taken in from water and the products have higher energy level than reactant, causing the temperature of water to decrease from 20 to 12⁰C.
ii. +13.4 Kj/mol
iii. potassium ions and chloride ions will separate and move between water molecules. The arrangement of particles will change from regular, very closely packed to random arrangement, closely packed. The movement of particles will change from vibrating in fixed positions to sliding past each other.
a) i. Fluorine is more reactive than bromine, chlorine displaces bromide ions from potassium bromide to form potassium fluoride and bromine. Presence of brown bromine dissolving in water accounts for solution turning brown. F2 (g) + 2Br-(aq) →2F-(aq) + Br2(aq)
ii. jet of chlorine gas will cause the colourless solution to turn brown. Chlorine is more reactive than bromine, chlorine displaces bromide ions from potassium bromide to form potassium chloride and bromine. Presence of brown bromine dissolving in water accounts for solution turning brown.
Bromine is more reactive than iodine thus iodine cannot displaces bromide ions from potassium bromide. However, Colourless solution turns yellow brown. This is due to some iodine gas dissolves in water in solution to form aqueous iodine. Aqueous iodine is yellow brown.
b) i. 3F2(g) + 2Fe(s) → 2FeF3 (s)
ii. Fluorine is an oxidising agent as it is reduced. Electrons is transferred from Fe to F2, this oxidises Fe to Fe3+ in FeCl3. F2 gains electrons to become F- in FeF3.
F2 increases the oxidation state of Iron in Fe to increases from 0 to +3 in FeF3. F2 is reduced as the oxidation state of fluorine decreases from 0 in F2 to -1 in FeF3.