General Principles and Processes of Isolation of Elements — Chemistry STD 12 Science — Question
Gujarat BoardEnglish MediumSTD 12 ScienceChemistryGeneral Principles and Processes of Isolation of Elements3 Marks
Question
Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.
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Answer
In the blast furnace, reduction of iron oxides takes place in different temperature ranges. Coke is burnt to get the required temperature upto about 2200K. The temperature is lower in the upper part. Hence, the reduction of iron oxides take place at lower portion.
The higher temperature range, depend on the points of corresponding intersections in the $\triangle rG^0$ vs T plots.
These reactions are as follows:
At $500 – 800K$ (lower temperature range in the blast furnace)-
$3Fe_2O_3 + CO → 2Fe_3O_4 + CO_2$
$Fe_3O_4 + 4CO → 3Fe + 4 CO_2$
$Fe_2O_3 + CO → 2FeO + CO_2$
At $900 – 1500K$ (higher temperature range in the blast furnace):
$C + CO_2 → 2CO$
$FeO + CO → Fe + CO_2$
The silicate impurity of the ore is removed as slag by calcium oxide $(CaO)$, which is formed by the decomposition of limestone $(CaCO_3).$