[INeedSerotonin]

Hello, everyone!

There is this exercise about the production of acetylene.



If we add CaC₂ and H₂O together, we will have acetylene and Ca(OH)₂. Ok, I know this. But the question is about the laboratory equipment.

My book says: fill with water (4) and (5); put water on (1); put CaC₂ on (2).

I don't understand the first step. Why should we fill with water (4) and (5) before everything? When water droplets leave (1) and fall on CaC₂, it makes acetylene. It is a gas, and it can't go back to (1), because water is dripping. So it goes though the hose up to (4). Where is my mistake?

Thanks

[Borek]

What would happen to the produced gas if the 4/5 are dry? Would you be able to collect it all?

[INeedSerotonin]

What would happen to the produced gas if the 4/5 are dry? Would you be able to collect it all?

I have no idea. I initially thought that the gas would occupy all of the space (that is, the hose and the cilinder). But I have no idea as for how the gas could be collected, whether with water or without it.   

Perhaps it has something to do with the pressure that the water exerts upon the hose and the cilinder. But I'm stuck here.

[Borek]

I initially thought that the gas would occupy all of the space (that is, the hose and the cilinder).

You think it wouldn't mix with the air?

And how would you be able to tell where is the boundary between your gas and the air?

[INeedSerotonin]

I initially thought that the gas would occupy all of the space (that is, the hose and the cilinder).

You think it wouldn't mix with the air?

And how would you be able to tell where is the boundary between your gas and the air?

I think I've understood now. The air is miscible with water, but acetylene is not (because water is polar, and acetylene is non-polar). So this is how we obtain pure acetylene.

But, after filling (4) and (5) with water, how can I transfer pure acetylene from inside (4) to, say, a bottle? Wouldn't a little bit of air always get inside the bottle together?

[Borek]

The air is miscible with water

Huh? What "miscible" means?

[INeedSerotonin]

The air is miscible with water

Huh? What "miscible" means?

Doesn't the water absorb some of the air? This is how the fish can breathe, isn't it?

[Borek]

What does "miscible" mean?

[INeedSerotonin]

What does "miscible" mean?

It means they form an homogeneous solution. Aren't they? I guess that it is a dispersion too, right? It's like sugar and water: they form an homogeneous solution, but it is not a new substance. The sugar is dispersed inside the water. In the same way, oxygen is dispersed inside water too.

[Borek]

What does "miscible" mean?

It means they form an homogeneous solution.

No. Every solution by definition is homogenous. Miscible means substances can be mixed in any proportions.

[INeedSerotonin]

What does "miscible" mean?

It means they form an homogeneous solution.

No. Every solution by definition is homogenous. Miscible means substances can be mixed in any proportions.

You're right! I didn't know that! So oxygen and water are not miscible, but they can become a mixture. Thank you!

[hypervalent_iodine]

What does "miscible" mean?

It means they form an homogeneous solution.

No. Every solution by definition is homogenous. Miscible means substances can be mixed in any proportions.

You're right! I didn't know that! So oxygen and water are not miscible, but they can become a mixture. Thank you!

Returning to the question though. What would happen to the acetylene gas if you didn't have any water in 4 or 5? Where would it go?

[INeedSerotonin]

What does "miscible" mean?

It means they form an homogeneous solution.

No. Every solution by definition is homogenous. Miscible means substances can be mixed in any proportions.

You're right! I didn't know that! So oxygen and water are not miscible, but they can become a mixture. Thank you!

Returning to the question though. What would happen to the acetylene gas if you didn't have any water in 4 or 5? Where would it go?

I think that it would make its way up to (4). The only difference is that now we wouldn't have pure acetylene. Am I correct?

I also am not sure as for the cylinder, but I think that both extremities are open. So I think that some of the acetylene would make its way back to (5), and it wouldn't take the path we want it to take.

[Borek]

I think that it would make its way up to (4). The only difference is that now we wouldn't have pure acetylene. Am I correct?

Even assuming that's what happens - how would you know where does the acetylene end and air starts, where is the boundary between both gases?

[INeedSerotonin]

I think that it would make its way up to (4). The only difference is that now we wouldn't have pure acetylene. Am I correct?

Even assuming that's what happens - how would you know where does the acetylene end and air starts, where is the boundary between both gases?

I wouldn't know. I think that there is no boundary. The gases always mix themselves. So water would show us that there is some gas being made. Is this the only purpose of the water?