0
$\begingroup$

In the book, Chemistry : A molecular approach, I came across this line:

enter image description here

Over here what does the author mean by work done by expanding against atmosphere?

$\endgroup$
2
$\begingroup$

Imagine someone was pushing you against a wall. If you spend some energy overcoming that push, wouldn't you say that you did some work (expenditure of energy) against that pressure?

With a similar line of reasoning, the atmosphere is exerting a pressure of one atmosphere trying to compress your gas down. That's a huge pressure (nearly $10^5$ pascals!) and the gas in question has expanded against it. The wording makes sense.

In general, whenever gases are produced as a result of some reaction (in this case combustion), they are initially at a higher pressure than atmospheric pressure. This isn't an equilibrium situation. So, they expand, and lose their pressure until it finally becomes equal to that of the atmosphere.

$\endgroup$
-1
$\begingroup$

It just means that when you burn natural gas, the reaction increases the volume of the matter involved in the reaction, so the system expands. The author's wording is odd when they said it expands "against the atmosphere"; that just means the atmosphere is always there, exerting pressure, but the system expands anyway.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.