Why Zn + Vinegar Gas Collecting Setup Cannot be Used for Preparing H2

[apchemstudent]

Why could you not use this setup for preparing H2 if the generator contained Zn + vinegar? It's in the attachment.


a) hydrgoen would not be produced.
b) the setup of the generator is improper.
c) the generator must be heated with a burner.
d) the delivery tube setup is wrong.
e) the gas cannot be collected over water.

Again please help. I think the answer is either b) or d)... but I'm not sure... thanks

 

[mrjeffy321]

I think it is (B), or possibly (D).

2 reasons for thinking this.
-1. if you look at the height that the gas comes out at the top of the bottle and up the tube before it slants over, this is higher than (or about equal to) the top of the bottle that it is collected in.
that is kinda like trying to cyphun a liquid up to a higher spot than it was originally, it won't ever go higher than it starts at, or in this case lower since hydrogen has a natural tendency to go up.

-2. my second reason in thinking (B) is that I have tried something similar to this myself in real life, and even with the collection bottle higher than everything else and trying to get the tube as striaght and easy for the gas to pass through, it would not work. I think it has something to with the water pressure pushing back on the hydrogen more than it wanted to go up, so in the end I never got any hydrogen in my collection bottle, and over the course of several hours, the hydrogen traveled a gran total of a few inches through the tube and then stopped and wouldn't move any more.