CSIR-NET/JRF 2014
The use of a dynamic inert atmosphere in thermogravimetric analysis (TGA):
- (a) Decreases decomposition temperature
- (b) Decrease weight loss
- (c) Reduces rate of decomposition
- (d) Increases weight loss
Correct Answer: (a) Decreases decomposition temperature
Explanation:
In TGA, the atmosphere significantly affects the decomposition kinetics of the sample.
Why the temperature decreases:
- A dynamic atmosphere (constantly flowing gas like N2 or Ar) sweeps away the gaseous products formed during decomposition as soon as they are released.
- According to Le Chatelier's Principle, the rapid removal of products shifts the equilibrium forward, allowing the reaction to proceed at a lower temperature compared to a static atmosphere.
- In a static atmosphere, the product gases linger around the sample, increasing the partial pressure of the products and inhibiting the decomposition, which effectively shifts the decomposition to a higher temperature.
Note: It does not change the total weight loss (b or d), as the stoichiometry of the reaction remains the same; it only changes when (at what temperature) that loss occurs.