Chemistry · Some Basic Concepts Of Chemistry · NEET
Coke is almost pure carbon (C). When CO2 gas touches hot carbon, the carbon pulls one oxygen away from CO2 and both become carbon monoxide. The balanced equation is CO2 + C -> 2CO. This only happens at high temperature (hot coke). It is a way to make CO gas.
Look at the gas molecules only. On the left you have 1 volume of CO2 gas. Carbon (C) is a solid, so it does NOT count as gas volume. On the right you get 2 volumes of CO gas. So 1 volume of gas becomes 2 volumes of gas. Every 1 dm3 of CO2 that reacts makes the total gas grow by 1 extra dm3.
Say x dm3 of CO2 reacts. It makes 2x dm3 of CO. The CO2 left over is (starting CO2 - x). Total gas = (leftover CO2) + (CO made). The increase in total volume is exactly equal to x, the amount of CO2 that reacted. So: volume increase = amount of CO2 reacted.
Start with the total CO2 (say 1 dm3). Let x = CO2 that reacts. Final total gas = 1 + x (because volume grows by x). If final total is given (like 1.4), then 1 + x = 1.4, so x = 0.4. CO made = 2x = 0.8 dm3. CO2 left = 1 - x = 1 - 0.4 = 0.6 dm3. Always check: 0.8 + 0.6 = 1.4. Correct.
No. Coke is a solid at these temperatures. In gas-volume stoichiometry (Gay-Lussac's law of gaseous volumes), you only count GASES. So CO2 and CO count, but solid carbon does not. This is why the volume changes even though atoms are conserved - the solid carbon leaves the gas phase and joins the gas as CO.
It is related but not the same. Producer gas is made by passing air (or CO2) over hot coke. The pure CO2 + C -> 2CO step here is the key reaction inside producer gas making. For NEET Some Basic Concepts, you only need this single balanced equation and the volume math, not the full industrial process.
When 1 dm3 of CO2 gas is passed over hot coke, the volume of the gaseous mixture after complete reaction at STP becomes 1.4 dm3. The composition of the gaseous mixture at STP is
Try the real previous-year questions from this chapter — each with the answer and a full solution.
CO2 + C -> 2CO. One molecule of carbon dioxide plus one atom of carbon gives two molecules of carbon monoxide. It needs high temperature (hot coke).
Coke is a cheap, nearly pure form of carbon used in industry. For the chemistry it is just carbon (C), so any elemental carbon would react the same way. NEET writes coke to sound like the real industrial process.
No. Atoms are always conserved. What changes is the gas VOLUME, because the solid carbon (no gas volume) becomes part of the gas as CO. Mass and atoms are conserved; gas volume is not.
Use one line: CO2 reacted = final total volume - starting CO2 volume. Then CO = 2 x reacted, and leftover CO2 = starting - reacted. This works because each dm3 reacted adds exactly 1 dm3 to the total.
It tests Gay-Lussac's law of gaseous volumes and simple stoichiometry from the Some Basic Concepts chapter. It appeared as a direct NEET 2026 question, so knowing the volume trick can win an easy mark fast.
