Suppose that 2.3 L of gas at 35°C and 1.0 atm is expanded to 4.5 L at 42°C. What will the final pressure of the gas be?
(Ti in Kelvins=308.15; Tf(K)=315.15)
Can someone please show me how to plug the values into the Combined Gas Law formula to calculate for Pf? Please don't perform any calculations. I want to figure it out by myself as I have many practice problems like it.
I just went and did the equation the way I think it goes. Please tell me if I am right:
(1*2.3L)/308.15=(Pf*4.5L)/315.15
so take 4.5L-2.3L=2.2L
then 2.3L/308.15(k)=(2.2*4.5L)/315.15(k)
2.3/308.15=9.9/315.15
final answer is
Pf=2.2
Did I do that right?
The set up is right. The algebra is not.
(1*2.3L)/308.15=(Pf*4.5L)/315.15
OK for set up You "cross multiply".
1*2.3*315.15 = Pf*4.5*308.15
Pf = 1*2.3*315.15/4.5*308.15
Pf = ?
so then:
1*2.3*315.15/Pf*4.5*308.15
Pf=2.38315.15/4.5*308.15
724.85/1386.68
Pf=0.52
ok, great! Thank you very much. I was adding an extra step by subtracting 2.3 from 4.5 and I have no idea why I did that.
To calculate the final pressure (Pf) of the gas using the Combined Gas Law formula, you can follow these steps:
1. Determine the given values:
- Initial volume (Vi) = 2.3 L
- Initial temperature (Ti) = 35°C (convert to Kelvin by adding 273.15: Ti = 35 + 273.15 = 308.15 K)
- Initial pressure (Pi) = 1.0 atm
- Final volume (Vf) = 4.5 L
- Final temperature (Tf) = 42°C (convert to Kelvin: Tf = 42 + 273.15 = 315.15 K)
2. Write down the Combined Gas Law formula:
Pi * Vi / Ti = Pf * Vf / Tf
3. Substitute the known values into the formula. It should look like this:
(1.0 atm) * (2.3 L) / (308.15 K) = Pf * (4.5 L) / (315.15 K)
4. Rearrange the formula to solve for Pf:
Pf = (Pi * Vi * Tf) / (Vf * Ti)
5. Plug in the values and simplify:
Pf = (1.0 atm * 2.3 L * 315.15 K) / (4.5 L * 308.15 K)
That's how you would set up the Combined Gas Law formula to calculate the final pressure (Pf) of the gas.