If 18 g of Kr initially at 0.5 bar and 18 L is brought to 0.49 bar and 5L, what is the overall change in enthalpy of this process? Assume that Kr is an ideal gas.

To find the overall change in enthalpy of this process, we need to calculate the change in internal energy.

The change in internal energy (ΔU) can be calculated using the ideal gas law equation:

ΔU = Δn * R * ΔT

Where:
- Δn is the change in the number of moles of gas.
- R is the ideal gas constant.
- ΔT is the change in temperature (which we assume to be constant in this case).

First, let's calculate the change in the number of moles of gas (Δn). We can use the ideal gas law equation in the form:

P * V = n * R * T

Where:
- P is the pressure.
- V is the volume.
- n is the number of moles of gas.
- R is the ideal gas constant.
- T is the temperature.

In the initial state:
P1 = 0.5 bar
V1 = 18 L

In the final state:
P2 = 0.49 bar
V2 = 5 L

Now, we can calculate the number of moles in each state:

n1 = (P1 * V1) / (R * T1)
n2 = (P2 * V2) / (R * T2)

Since the temperature remains constant, T1 = T2, so we can simplify to:

n1 = (P1 * V1) / (R * T)
n2 = (P2 * V2) / (R * T)

Where T is the common temperature in both states.

Next, we calculate the change in moles:

Δn = n2 - n1

Now that we have Δn, we can calculate the change in internal energy (ΔU) using the ideal gas law equation mentioned before:

ΔU = Δn * R * ΔT

Since ΔT is assumed to be constant, we can simplify to:

ΔU = ΔP * ΔV

Where ΔP is the change in pressure and ΔV is the change in volume.

Now, substitute the values:

ΔP = P2 - P1 = 0.49 bar - 0.5 bar = -0.01 bar
ΔV = V2 - V1 = 5 L - 18 L = -13 L

Finally, calculate ΔU:

ΔU = (-0.01 bar) * (-13 L)

You can multiply the two values to obtain the overall change in enthalpy.