Video Transcript
Which of the following reactions,
which occurs inside the blast furnace, is exothermic and helps to keep the
temperature inside the furnace above 2,000 degrees Celsius? (A) Two CO reacts to produce CO2
plus C. (B) CaO plus SiO2 react to produce
CaSiO3. (C) CaCO3 reacts to produce CaO
plus CO2. (D) CO2 plus C react to produce two
CO. Or (E) C plus O2 react to produce
CO2.
Blast furnaces are steel towers
lined with heat-resistant bricks that can be used to extract iron from its ore. Before the iron ore is added to the
furnace, it is crushed, roasted, and mixed with coke and limestone. Together, these three substances
make up what is called the charge. The charge is added to the top of
the blast furnace, and hot air is blasted into the furnace from the bottom. Multiple chemical reactions happen
concurrently inside the blast furnace. Let’s examine each of these
reactions so that we can more easily understand the iron extraction process.
Coke is a substance that is almost
100 percent pure carbon. The carbon from the coke reacts
with hot air to produce carbon dioxide. This reaction is highly exothermic
and releases a lot of energy in the form of heat. The carbon dioxide gas can react
with additional coke to produce carbon monoxide gas. Carbon monoxide gas acts as a
reducing agent as it travels through the blast furnace, reducing iron oxide found in
the iron ore to molten iron.
Limestone is mostly made up of
calcium carbonate. Inside the blast furnace, the
calcium carbonate decomposes into calcium oxide and carbon dioxide. The calcium oxide can then react
with sandy impurities, which can be thought of as silicon dioxide to produce calcium
silicate. Calcium silicate is the main
component of a byproduct called slag.
Now that we’ve looked at the
reactions which occur inside a blast furnace, we need to determine which of these
reactions is exothermic and helps to keep the temperature inside the furnace above
2,000 degrees Celsius. An exothermic reaction is a
reaction that releases energy, often in the form of heat. We can see that the reaction
between carbon and oxygen releases energy in the form of heat. And we stated earlier that this
reaction is highly exothermic.
Therefore, the reaction inside of a
blast furnace that is exothermic and helps to keep the temperature inside the
furnace above 2,000 degrees Celsius is answer choice (E), C plus O2 react to produce
CO2.
