Heyy, I posted this before but it kinda got pushed down and ignored, and I was hoping maybe DrBob might have an idea since no one else did! okay I have this question about chemistry and its driving me nuts. It feels like I am so close but am just missing something. The question is:
A vessel of 6.84 L in volume contains 3.61 L of pure water at 25°C. A partial pressure of 3.67 atm of CO2 is quickly injected into the space above the water. Calculate the partial pressure of carbon dioxide remaining once the solution has become saturated with the gas. Henry's constant for CO2 at this temperature is 0.0350 M atm-1
Okay so I know basically this...we dicussed with some other people and rearrganed equations and basically got this:
(mol initial - mol final)/V = concentration x pressure.
so the initial moles you get using PV=NRT, so N=PV/RT and same for moles final (diff volumes used of course) but I think that's where I'm messing up. Because after that you divide by a volume, then by the concentration. But I think I'm messing up what volumes go where. I know what the answer ius supposed to be and I cant get it for the life of me. I'm thinking that for inital moles the volume would be 6.84 cause that's the whole thing. And then I'm thinking for final moles it would be 3.61 cause that's where the liquid is. But I don't know what I would divde by...the leftover 3.23? anyways I've tried many combinations and I cant get it. ANy help would be greatly apprecaited. I could be totally on the wrong track. Thanks
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Subject: Chemistry
To solve this problem, you need to use Henry's law, which states that the partial pressure of a gas above a liquid is proportional to the concentration of the gas in the liquid.
Here are the steps to solve the problem:
1. Calculate the initial moles of CO2:
- Use the ideal gas law equation PV = nRT to find the number of moles (n) of CO2 initially present in the vessel.
- Plug in the given values: P = 3.67 atm, V = 6.84 L, T = 25°C (convert to Kelvin by adding 273.15).
- Solve for n.
2. Calculate the concentration (C) of CO2 in the water:
- The concentration is given by the formula C = n/V, where n is the number of moles and V is the volume of the solvent (water).
- Calculate C using the initial moles of CO2 and the volume of water given (3.61 L).
3. Use Henry's law equation to find the final moles of CO2 in the system:
- The equation is P = kC, where P is the partial pressure of CO2 remaining, k is Henry's constant, and C is the concentration of CO2 in the water.
- Rearrange the equation to solve for the final moles: n_final = P/k.
4. Calculate the partial pressure (P_final) of CO2 remaining:
- Use the ideal gas law equation PV = nRT, where n is the final moles of CO2, T is the temperature (25°C converted to Kelvin), and V is the volume of the gas phase (the remaining volume in the vessel, 3.23 L).
- Solve for P_final.
By following these steps, you should be able to calculate the partial pressure of carbon dioxide remaining once the solution has become saturated with the gas. Make sure to double-check your calculations and units to ensure accuracy.