Animated Solution for Chemistry - s and p-Block Elements: The equation that represents the water-gas shift reaction is

Welcome to one of the most crucial chemical reactions in modern industry! As the world moves towards cleaner energy, hydrogen gas ($H_2$) is often hailed as the fuel of the future. However, pure hydrogen doesn't just float around in the atmosphere waiting to be bottled. We have to manufacture it.

One of the primary ways we get hydrogen is by processing fossil fuels or biomass. But these initial processes don't give us pure hydrogen; they give us a mixture of gases, primarily carbon monoxide ($CO$) and hydrogen ($H_2$). This mixture is famously known as Synthesis Gas or Syngas.

While syngas is useful, carbon monoxide is highly toxic and often an unwanted byproduct when our main goal is to harvest pure hydrogen for fuel cells or ammonia synthesis. So, how do we get rid of the toxic $CO$ and squeeze out even more $H_2$? Enter the Water-Gas Shift Reaction.

The Water-Gas Shift Reaction

The water-gas shift reaction is an elegant piece of chemical engineering. It takes the carbon monoxide from our syngas and reacts it with steam (water vapor).

Imagine the molecules colliding in a massive industrial reactor. The reaction requires a significant amount of heat, typically around $673\text{ K}$, and a specialized catalyst (usually an iron-chromium or copper-zinc mixture) to proceed at a useful rate.

Under these intense conditions, a beautiful atomic exchange occurs. The oxygen atom from the water molecule ($H_{2}O$) literally shifts over to the carbon monoxide ($CO$).

This single shift achieves two incredible things simultaneously: 1. It transforms the toxic $CO$ into carbon dioxide ($C{O}_2$), which can be easily scrubbed or separated from the gas mixture. 2. It strips the oxygen away from the water, liberating pure hydrogen gas ($H_2$)!

The master equation for this process is:

Now that we understand the chemistry, let's look at the options provided in the question. This is a classic JEE trap where all the options represent real, important industrial reactions, but only one is the shift reaction.

Option (a): $C(s)+H_{2}O(g)\stackrel{1270\text{ K}}{\to }CO(g)+H_2(g)$ This is the Coal Gasification reaction. Red-hot coke (carbon) reacts with steam to produce syngas (water gas). This is the step before the shift reaction. It creates the $CO$ we want to get rid of!

Option (b): $2C(s)+O_2(g)+4N_2(g)\stackrel{1273\text{ K}}{\to }2CO(g)+4N_2(g)$ This represents the formation of Producer Gas, a mixture of carbon monoxide and nitrogen. It has nothing to do with shifting water.

Option (d): $C{H}_4(g)+H_{2}O(g)\underset{Ni}{\overset{1270\text{ K}}{\to }}CO(g)+3H_2(g)$ This is Steam Reforming of Methane. Like coal gasification, this is a primary method to produce syngas. Notice how it produces $CO$ and $H_2$. Again, this is the precursor step, not the shift reaction itself.

Option (c): $CO(g)+H_{2}O(g)\underset{Catalyst}{\overset{673\text{ K}}{\to }}C{O}_2(g)+H_2(g)$ This is our winner! It perfectly shows carbon monoxide reacting with steam in the presence of a catalyst at $673\text{ K}$ to yield carbon dioxide and additional hydrogen.

By mastering the water-gas shift reaction, chemical engineers can maximize the yield of hydrogen from any carbon-based feedstock. This hydrogen is then purified and sent off to synthesize ammonia for global agriculture (the Haber process) or used to power the next generation of hydrogen fuel cell vehicles. It is a perfect example of how a simple atomic shift can power the world!