Gchem Questions

[LoLPoPs]

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1) What is the percentage of oxygen by mass in a 200 gram sample of CuSO4*5H2O?

2) What volume of hydrogen gase, in liters, at 40C and 763 torr can be produced by the complete reaction of 5.05 grams of zinc with excess HCl?

3) Increasing the amount of liquid in a sealed container will cause the vapor pressure of the liquid to...

The answer is : remain the same, regardless of the identity of the liquid.
But I thought the vapor pressure would decrease. Can someone explain why the answer is correct?

Thank you!!!😍

 

[RCT PC CRN]

1) It seems to be straight forward Q - mass of O/total mass. I'm not sure even you need that 200 g cause it's asking % only. You could go bit further and could find mass. Multiply % by 200 g and you will get mass of Oxygen in that hydrate.

2) This seems to be straight forward as well..Zn + 2HCl -> ZnCl2 + H2 you have g of Zn..turn that into mole..1 mole of Zn = 1 mole of H2...get mole of H2 = n and then PV=nRT...p=atm 763/760, T=kelvin (40+273)

3) This is how far my chem knowledge will take me...VP depends on Intermolecular force ..if you add or take out any liquid, It will not change Intermolecular force and thus VP will stay as it is. If you could change IF then you will change VP ..like adding some kind of solute.

Hope this helps.

 

[LoLPoPs]

1) It seems to be straight forward Q - mass of O/total mass. I'm not sure even you need that 200 g cause it's asking % only. You could go bit further and could find mass. Multiply % by 200 g and you will get mass of Oxygen in that hydrate.

2) This seems to be straight forward as well..Zn + 2HCl -> ZnCl2 + H2 you have g of Zn..turn that into mole..1 mole of Zn = 1 mole of H2...get mole of H2 = n and then PV=nRT...p=atm 763/760, T=kelvin (40+273)

3) This is how far my chem knowledge will take me...VP depends on Intermolecular force ..if you add or take out any liquid, It will not change Intermolecular force and thus VP will stay as it is. If you could change IF then you will change VP ..like adding some kind of solute.

Hope this helps.

Heyyy thank you sooooo much!!! That was very helpful!!!😍
That 200g from the first question just threw me off...and I thought I'm missing something... but I guess that information was unnecessary!

Thanks again!!! 🙂

 

[nyr201]

1) What is the percentage of oxygen by mass in a 200 gram sample of CuSO4*5H2O?

2) What volume of hydrogen gase, in liters, at 40C and 763 torr can be produced by the complete reaction of 5.05 grams of zinc with excess HCl?

3) Increasing the amount of liquid in a sealed container will cause the vapor pressure of the liquid to...

The answer is : remain the same, regardless of the identity of the liquid.
But I thought the vapor pressure would decrease. Can someone explain why the answer is correct?

Thank you!!!😍

VP in a sealed container is only dependent on temperature 😀

 

[nyr201]

1) It seems to be straight forward Q - mass of O/total mass. I'm not sure even you need that 200 g cause it's asking % only. You could go bit further and could find mass. Multiply % by 200 g and you will get mass of Oxygen in that hydrate.

2) This seems to be straight forward as well..Zn + 2HCl -> ZnCl2 + H2 you have g of Zn..turn that into mole..1 mole of Zn = 1 mole of H2...get mole of H2 = n and then PV=nRT...p=atm 763/760, T=kelvin (40+273)

3) This is how far my chem knowledge will take me...VP depends on Intermolecular force ..if you add or take out any liquid, It will not change Intermolecular force and thus VP will stay as it is. If you could change IF then you will change VP ..like adding some kind of solute.

Hope this helps.

hey RCT, do u get ~22.5 L for # 2?

 

[doglovernonesto]

I got 2.07 L...with a calculator. The numbers don't quite cancel easily - any other way to do it?

V=nRT/P
=(5.05/65.4) x 0.0861 x 313 x (760/763)