(Photo credit Ingy The Wingy)
Besides sharing Chemistry Tips and Exam Strategies, the other aim of this chemistry blogsite is to encourage students to learn the Chemistry Theories and Concepts in a more experiential and interesting way – HOW ? By relating chemistry theories to everyday life processes and experience.
Thermit Process came to my mind several days back when i was passing by the railway track in the west area of Singapore, and today i am going to share with you more on how Thermit Process – which is a highly exothermic reaction is used to weld together steel railway lines. It involves the reduction of iron (III) oxide to iron by aluminium.
Now, let’s check out a chemistry question that requires your concepts in several chemistry topics, namely:
- Energy Changes (Endothermic/Exothermic Reactions)
- Redox (Oxidation/Reduction)
- Mole Calculations
Question:
In the highly exothermic Thermit Process to weld railway lines, aluminium is used to reduce iron (III) oxide to iron based on the balanced chemical equation below:
2Al?? +?? Fe2O3 -> ? Al2O3 + ? 2Fe
(a) Indicate the state symbols for all the reactants and products involved
(b) Calculate what mass of aluminium is needed to react completely with 10.0g of iron (III) oxide
(c) Explain what is meant by exothermic reaction in terms of enthalpy change
(d) Explain in terms of oxidation state, how is iron (III) oxide being reduced in Thermit Process
Alright, do attempt the question and leave your answers in the comment section below. I would love to hear from you.
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a) state of aluminium is solid and that of iron (lll) oxide is also solid…
( this iron (lll) oxide is the common rust ) 🙂
for the products
Al2O3 I solid and iron is molten i-e liquid because it was mentioned that the reaction is highly exothermic …… 🙂
b) mass of iron (lll) oxide = 10g
realtive formula mass of iron (lll) oxide = 56×2 + 16×3
= 160
so,
moles of iron (lll)oxide = 10/160
= 0.0625 moles
keeping in view the stochiometric ratios of the reactants and the products we get that to react with one mole of Fe2O3 we need two moles of Al
so moles of Al used = 2x 0.0625
=.125 moles
now mass of Al = ?
= moles x molar mass
= .125 x 13
= 1.625 g
c) energy released in bond formation is more than the energy used in bond breaking
d) iron (lll) is gaining electrons and changing from Fe +3 to Fe 0….
as gain of electrons reduction so we term it as iron is reduced
🙂
moles in Fe2O3 : 10 / (55.8×2)+(16×3) = 0.06 mols
moles in Al : 0.06×2 = 0.12 mols
mass= moles x RMM = 0.12 x 27
= 3.24g of Al