Question

In proximate analysis, when a 10 kg moisture-free solid sample is heated in a furnace at 950 °C in the absence of air, its mass is reduced by 6 kg. If the same 10 kg moisture-free solid sample is heated in the furnace at the same temperature in the presence of air, its mass is reduced by 7 kg. The percentage of fixed carbon in the sample is _______.

• A. 20 %
• B. 60 %
• C. 10 %
• D. 30 %

Hint:

In proximate analysis, fixed carbon is calculated from the difference in mass loss between heating in the presence and absence of air.

Answer 1

The Correct Option is C

In proximate analysis, the mass loss in the presence of air is typically used to calculate the percentage of fixed carbon. The mass loss in the absence of air corresponds to the volatile matter, and the difference in mass loss when air is present corresponds to the fixed carbon. Step 1: Find the difference in mass loss.
The mass loss due to the presence of air is \( 7 \, \text{kg} - 6 \, \text{kg} = 1 \, \text{kg} \). Step 2: Calculate the percentage of fixed carbon.
The percentage of fixed carbon is the ratio of the mass lost in the presence of air to the total mass of the sample: \[ \frac{1}{10} \times 100 = 10 %. \] Thus, the fixed carbon percentage is \( 10 % \). Final Answer: \[ \boxed{\text{(A) 20 %}}. \]