A gas is compressed from 73.7 L to 1.9 L at 0.70 atmospheres? In addition a total of 4400 J of heat are gained from warmer surroundings. What is the change in internal energy in kJ?
I have a general idea of how to do this, but I tried and got -2851.8, which isn't right.
What is the enthalpy change (in kJ) for burning 3.20 g of ethyl alcohol?
I got 94.95 which apparently isn't right.
Please help!
To find the change in internal energy, we can use the formula:
ΔU = q + w
Where ΔU is the change in internal energy, q is the heat gained or lost, and w is the work done.
In this case, we are given the heat gained (q = 4400 J), but we need to determine the work done. The work done can be calculated using the formula:
w = -PΔV
Where P is the pressure and ΔV is the change in volume.
Given:
Initial volume (V1) = 73.7 L
Final volume (V2) = 1.9 L
Pressure (P) = 0.70 atm
First, we need to convert the pressure from atm to Pa (since the SI unit is Pascal).
1 atm = 101325 Pa
So, P = 0.70 atm * 101325 Pa/atm = 70927.5 Pa
Next, we calculate the change in volume:
ΔV = V2 - V1 = 1.9 L - 73.7 L = -71.8 L
We need to convert the change in volume to m³ (since the SI unit is cubic meters).
1 L = 0.001 m³
So, ΔV = -71.8 L * 0.001 m³/L = -0.0718 m³
Now we can calculate the work done:
w = -PΔV = -70927.5 Pa * (-0.0718 m³) = 5096.13 J
Finally, we can calculate the change in internal energy:
ΔU = q + w = 4400 J + 5096.13 J = 9496.13 J
To convert this to kJ, we divide by 1000:
ΔU = 9496.13 J / 1000 = 9.49613 kJ
Therefore, the change in internal energy is approximately 9.496 kJ.
For the second question regarding the enthalpy change in burning ethyl alcohol:
To calculate the enthalpy change, we need to know the balanced chemical equation for the combustion of ethyl alcohol (C2H5OH). Without the equation, it is not possible to determine the enthalpy change as it depends on the specific reaction.
Please provide the balanced chemical equation for the combustion of ethyl alcohol, and I can guide you through the calculations.