Temperature, state of matter (gas/liquid/solid), relative molecular mass
Category: FAQs
List 3 examples of substances that sublimes.
Ammonium chloride, iodine crystals, dry ice, naphthalene.
List examples of 3 gases that are very soluble in water.
Ammonia, sulfur dioxide, hydrogen chloride
List 3 common catalysts used in industrial processes.
– iron: in Haber Process, to manufacture ammonia
– vanadium(V) oxide: in manufacture of sulfuric acid
– platinum or rhodium: in catalytic converters
– aluminium oxide or silicon(IV) oxide: in the cracking process for producing hydrogen
Write down the anode reaction, cathode reaction, and overall reaction of a hydrogen fuel cell.
Anode: 2H2 (g) + 4OH– (aq) –> 4H2O (l)+ 4e–
Cathode: O2(g) + 2H2O (l) + 4e– –> 4OH– (aq)
Overall: 2H2(g) + O2(g) –> 2H2O (l)
List 3 examples of exothermic reactions, and 3 examples of endothermic reactions.
Examples of exothermic reactions are:
– combustion of fuels
– rusting of iron
– neutralisation reaction
Examples of endothermic reactions are:
– photosynthesis
– thermal decomposition
– dissolving of some ionic compounds in water (eg NH4Cl)
This reaction, CH4 + 2O2 –> CO2 + 2H2O, is exothermic. Describe this exothermic reaction in terms of energy involved in bond breaking and bond making.
The heat energy absorbed to break the bonds in CH4 and 2O2 is less than the heat energy released to form the bonds in CO2 and 2H2O, so overall enthalpy change is negative.
Write down the 5 reactions in the blast furnace for the extraction of iron from haematite.
C (s) + O2 (g) –> CO2 (g)
CaCO3 (s) –> CaO (s) + CO2 (g)
C (s) + CO2 (g) –> 2CO (g)
Fe2O3 (s) + 3CO (g) –> 2Fe (l) + 3CO2 (g)
CaO (s) + SiO2 (s) –> CaSiO3 (l)
Give 3 advantages of recycling metals.
It helps to reduce pollution. Extraction of metals from their ores produces much more air, land and water pollution compared to recycling of metals.
It conserves energy resources. Extraction of metals from their ores uses up much more energy compared to recycling of metals.
It conserves limited land resources. Metal mining and smelting processes use up large area of land. Recycling metals reduces the need for these metal mines, and free up the land for alternative uses.
Explain why, going from left to right in the same Period, the atomic radii of the element decrease.
Elements in the same Period have the same number of electronic shells, but the proton number of the elements increase from left to right.
As number of protons increase, the attractive force of the positive protons on the negative electrons also increases, pulling the electronic shells closer together.
Hence atomic radius decreases from left to right in the same Period.