Help me with GC questions!

[d wannabe]

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1. Into a two liter vessel, containing a gas at 0.8 atmospheric pressure, 400mL of mercury is injected. What would be the new pressure? (There is no evidence of a chemical reaction)

The answer is 1atm. Can somebody explain how to get 1atm?

 

[Thundercatz]

1. Into a two liter vessel, containing a gas at 0.8 atmospheric pressure, 400mL of mercury is injected. What would be the new pressure? (There is no evidence of a chemical reaction)

The answer is 1atm. Can somebody explain how to get 1atm?

You have a 2L vessel with .8 atm. Now you poor in 400ml of mercury, this will reduce the new volume to 1.6L (2L - .4L). Using P1V1 = P2V2, you have (2)(.8) = (1.6)(x) = 1.

 

[billythekid]

Yeah, thundercatz is right. Use P1V1/P2V2

 

[wifi08]

dont forget that formula man especially the one where p1v1/t1=p2v2/t2

 

[DentalDeac]

Yeah but you are adding 400 mL of gas so shouldn't the total volume now be 2.4 instead of 1.6? I dont understand how you did that Thundercatz.

 

[PooyaH]

Yeah but you are adding 400 mL of gas so shouldn't the total volume now be 2.4 instead of 1.6? I dont understand how you did that Thundercatz.

Well is it mercury gas or just mercury?

 

[Thundercatz]

Yeah but you are adding 400 mL of gas so shouldn't the total volume now be 2.4 instead of 1.6? I dont understand how you did that Thundercatz.

Read the question again. It stats that there was .8 atm of pressure in a 2 liter vessel. Mean the vessel was empty. Now you pour 400ml of a liquid into the vessel, so the volume decreased. Imagine having an empty two liter bottle of a coke, now you pour in 400ml of water in it. Would the volume of the 2 liter coke decrease or increase?

 

[doc toothache]

Yeah but you are adding 400 mL of gas so shouldn't the total volume now be 2.4 instead of 1.6? I dont understand how you did that Thundercatz.

We are dealing with a closed container.

Well is it mercury gas or just mercury?

Mercury boils at 357 C so we are probably dealing with the liquid.

 

[PooyaH]

Mercury boils at 357 C so we are probably dealing with the liquid.

haha true that!

 

[klutzy1987]

Yes but the question never accounts for the vapor pressure coming from the mercury which will raise the pressure even more. Really this is no correct answer for this question.

 

[doc toothache]

Yes but the question never accounts for the vapor pressure coming from the mercury which will raise the pressure even more. Really this is no correct answer for this question.

At 20 C the vapor pressure of mercury is 1.2microm Hg.