Q1: Volumetric composition of flue gas analysed with the Orsat apparatus is : CO₂ = 12%, O₂ = 8%, CO = nil, N₂ = 80%. This flue gas composition indicates that

ANS:C - excess air has been used for combustion.

Based on the volumetric composition of the flue gas analyzed with the Orsat apparatus:

• CO2=12%CO2​=12%
• O2=8%O2​=8%
• CO=nilCO=nil (indicating no carbon monoxide)
• N2=80%N2​=80%

We can make the following observations:

1. Oxygen Content: The presence of oxygen (O2=8%O2​=8%) in the flue gas indicates that excess air has been used for combustion. Incomplete combustion would result in the presence of unburned oxygen or carbon monoxide in the flue gas, which is not the case here.
2. Nitrogen Content: The majority of the flue gas composition is nitrogen (N2=80%N2​=80%). This is expected since air primarily consists of nitrogen. The high nitrogen content does not necessarily indicate a high percentage of nitrogen in the fuel, but rather it reflects the composition of the air used for combustion.
3. Carbon Monoxide Content: The absence of carbon monoxide (CO=nilCO=nil) suggests complete combustion of the fuel. If carbon monoxide were present, it would indicate incomplete combustion.
4. Carbon Dioxide Content: The presence of carbon dioxide (CO2=12%CO2​=12%) is typical in the flue gas resulting from combustion processes. It is a byproduct of complete combustion.

Based on these observations, the flue gas composition indicates that excess air has been used for combustion. This is supported by the presence of oxygen and the absence of carbon monoxide, suggesting that combustion was well-aerated. Additionally, the high nitrogen content is expected due to the use of air as the oxidizer. Therefore, the correct interpretation is that excess air has been used for combustion.