Vanadium is commonly found in different ores such as magnetite, vanadinite and patronite. The vanadium is commonly extracted from these ores by reduction and displacement.
Vanadium can be extracted by the reduction of vanadium pentoxide, V2O5, with calcium at high temperatures, according to the following equation.
V2O5 (s) + 5Ca (s) → 2V (s) + 5CaO (s)
The enthalpy of formation of vanadium pentoxide is -1560 kJ mol-1 and the standard enthalpy change for the reaction is -1615 kJ mol-1.
Blending amounts of alternative fuel with conventional fuel is one way to replace petroleum. A fuel blend of 51% to 83% ethanol and the remaining being gasoline is known as E85.
If the fuel blend is vaporised before combustion, predict whether the amount of energy released would be greater, less or the same. Explain your answer.
Strontium salts have a number of applications such as fireworks, flares, glow in the dark paint and toothpaste for sensitive teeth. The strontium required for these salts can be extracted from the ore strontia, SrO, by displacement with powdered aluminium in a vacuum.
i)
Write a balanced symbol equation, including state symbols, for the reaction of strontia with aluminium.
The standard enthalpy change for this extraction of strontium is 99.3 kJ mol-1 and the standard enthalpy of formation of aluminium oxide is -1676.7 kJ mol-1
Use this information to calculate the standard enthalpy of formation, ΔHf, in kJ mol-1 of strontia.
Manganese is too brittle for use as a pure metal, so it is often alloyed with other metals. Manganese is used in steel to increase the strength and resistance to wear. Manganese steel (13% Mn) is extremely strong and used for railway tracks, safes and prison bars. Alloys of 1.5% manganese with aluminium are used to make drinks cans due to the improved corrosion resistance of the alloy.
Manganese is extracted from different ores by reduction with carbon monoxide.
Mn2O3(s) + 3CO (g) → 2Mn (s) + 3CO2(g)
The enthalpy of formation, ΔHf, of Mn2O3 (s) is −971 kJ mol-1. Use this information and section 12 of the data booklet to calculate the enthalpy change of reaction, ΔHr, in kJ mol-1.
The reaction in part c) reaches equilibrium at high temperatures.
Use your answer to part c) to explain how temperature can be altered to increase the yield of the reaction and explain the effect that this would have on the rate of reaction.
