Hi!
I have another question.
So 1 kcal of heat is added to 1.5 L of oxygen in a container at constant pressure. (1atm). Then volume increases to 3.1L. they want to know total energy change.
Now i think the formula is DH=DU + PDV
so what i did was DH = 1 kcal + 1atm(3.1-1.5) = 2.6 kcal...
its wrong... i don't know why please help!
thanks again!
Hi there! I'd be happy to help you with your question.
The formula you mentioned, DH = DU + PDV, is indeed the correct equation for calculating the total energy change (DH) in a system. However, it seems like there might be a small mistake in the values you used.
Let's go through the steps together to correct it:
Step 1: Given information
- Heat added (Q) = 1 kcal
- Change in volume (DV) = 3.1 L - 1.5 L = 1.6 L
- Pressure (P) = 1 atm
Step 2: Calculate the work done (PDV)
The work done is given by the product of pressure and change in volume: PDV = (1 atm) * (1.6 L).
Note: It's important to make sure that the units are consistent. The units of pressure and volume must match.
Step 3: Calculate the change in internal energy (DU)
The change in internal energy (DU) is equal to the heat added (Q) minus the work done (PDV): DU = Q - PDV.
Using the given values, the change in internal energy (DU) can be calculated as:
DU = (1 kcal) - (1 atm) * (1.6 L).
Step 4: Calculate the total energy change (DH)
The total energy change (DH) is the sum of the change in internal energy (DU) and the work done (PDV): DH = DU + PDV.
Now, let's calculate the values:
PDV = (1 atm) * (1.6 L) = 1.6 atm·L
DU = (1 kcal) - (1 atm) * (1.6 L) = 1 kcal - 1.6 atm·L
DH = (1 kcal - 1.6 atm·L) + (1.6 atm·L) = 1 kcal.
Therefore, the correct total energy change (DH) is 1 kcal.
I hope this clarifies the calculation for you! Let me know if you have any further questions.