Help needed for Gen Chem 2 probs!

[Swenis]

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Hi everyone 🙂

I'm in the first week of my summer general chemistry 2 class, and I have a few questions about some practice problems that are giving me trouble. I have a quiz tomorrow so I'm trying to get everything ingrained to memory. If you all could help me with these few and explain how, I would be evermost gracious! Thank you all! 😍

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1) The cooling system of a car is filled with a solution formed by mixing equal volumes of water (density = 1g/1mL) and ethylene glycol, C2H6O2 (density = 1.12g/1mL). Estimate the freezing point and boiling point of the solution.

I calculated 109.21 oC for the boiling point and -1.68 oC for the freezing point.
Can anyone verify this?

2) a) A sample of H2 gas is generated in a closed container by reacting 2.050g Zn(s) with 15.0 mL of 1.00M H2SO4. Write the balanced equation for the reaction, and calculate the number of moles of H2 (g) formed, assuming the reaction is complete.

b) The volume over a solution is 122 mL. Calculate the partial pressure of the gas in the solution.

c) The Henry's law constant for hydrogen gas in water at 25 oC is 7.8E-4 mol/L-atm. Estimate the number of moles of hydrogen gas that remain dissolved in the solution. What fraction of the gas molecules is dissolved in solution?

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I'm sorry for all the typing, but I have been working on pages of problems for like six hours, and I don't know these last ones. Any help is very appreciated!

 

[Requiem]

Sorry I have no calculator or textbook nearby, only my memory haha.

) The cooling system of a car is filled with a solution formed by mixing equal volumes of water (density = 1g/1mL) and ethylene glycol, C2H6O2 (density = 1.12g/1mL). Estimate the freezing point and boiling point of the solution.

I calculated 109.21 oC for the boiling point and -1.68 oC for the freezing point.
Can anyone verify this?


I'm not sure of the original boiling points of these liquids, should be a straightforward formula calculation i.e just simply look up another similar example. Adding substances to a liquid increases it's BP.

2) a) A sample of H2 gas is generated in a closed container by reacting 2.050g Zn(s) with 15.0 mL of 1.00M H2SO4. Write the balanced equation for the reaction, and calculate the number of moles of H2 (g) formed, assuming the reaction is complete.

Zn(s) + H2SO4(l) -> H2(g) + ZnSO4 (aq) I know SO4 is 2-, pretty sure Zn is 2+. if not, just simply balance as such.

b) The volume over a solution is 122 mL. Calculate the partial pressure of the gas in the solution.

PV = nRT. volume 122ml, mols = 2.050g / M R = constant T = 298k

c) The Henry's law constant for hydrogen gas in water at 25 oC is 7.8E-4 mol/L-atm. Estimate the number of moles of hydrogen gas that remain dissolved in the solution. What fraction of the gas molecules is dissolved in solution

From your pressure solved in part B), find the # of mols dissolved. From this # of mols, do a simple mol fraction of mol dissolved/total mol.



Kinda rushed and very skimpy replies, but this isn't tough stuff you should be able to look up similar examples and just get the formulas / calculations figured out. I wouldn't worry, very minor 'plug n chug'.

 

[mystiqx]

Hi everyone 🙂

I'm in the first week of my summer general chemistry 2 class, and I have a few questions about some practice problems that are giving me trouble. I have a quiz tomorrow so I'm trying to get everything ingrained to memory. If you all could help me with these few and explain how, I would be evermost gracious! Thank you all! 😍

---------------------------------------------------------------------------
1) The cooling system of a car is filled with a solution formed by mixing equal volumes of water (density = 1g/1mL) and ethylene glycol, C2H6O2 (density = 1.12g/1mL). Estimate the freezing point and boiling point of the solution.

I calculated 109.21 oC for the boiling point and -1.68 oC for the freezing point.
Can anyone verify this?

2) a) A sample of H2 gas is generated in a closed container by reacting 2.050g Zn(s) with 15.0 mL of 1.00M H2SO4. Write the balanced equation for the reaction, and calculate the number of moles of H2 (g) formed, assuming the reaction is complete.

b) The volume over a solution is 122 mL. Calculate the partial pressure of the gas in the solution.

c) The Henry's law constant for hydrogen gas in water at 25 oC is 7.8E-4 mol/L-atm. Estimate the number of moles of hydrogen gas that remain dissolved in the solution. What fraction of the gas molecules is dissolved in solution?

---------------------------------------------------------------------------

I'm sorry for all the typing, but I have been working on pages of problems for like six hours, and I don't know these last ones. Any help is very appreciated!

Hi Swenis
There is a thread called Science in the PCAT section that has a link to another thread where you can post you questions to any General chemistry question you have and get answers to them, you should check that out maybe it will help as well and good luck on your quiz tomorrow

~M

 

[Swenis]

Thank you all!