Full Text
```python
import math
class Gas:
R = 8.314 # Ideal gas constant in J/(mol·K)
def __init__(self, temp=None, pressure=None, volume=None, moles=None, molecular_weight=None,
temp_unit="K", pressure_unit="Pa", volume_unit="m^3"):
self._temp = None
self._pressure = None
self._volume = None
self._moles = None
self._molecular_weight = None
self._density = None
# Store initial units for potential future use (though get_ methods have defaults)
self._temp_init_unit = temp_unit
self._pressure_init_unit = pressure_unit
self._volume_init_unit = volume_unit
# Convert initial values to default units (Kelvin, Pascal, m^3) and set
if temp is not None:
self.temperature = self._convert_temp(temp, temp_unit, "K")
if pressure is not None:
self.pressure = self._convert_pressure(pressure, pressure_unit, "Pa")
if volume is not None:
self.volume = self._convert_volume(volume, volume_unit, "m^3")
if moles is not None:
self.moles = moles # moles is already in default unit (mol)
if molecular_weight is not None:
self.molecular_weight = molecular_weight # molecular_weight is in g/mol
# Recalculate any missing P, V, T, n and then density
self._recalculate_state()
self._calculate_density()
@staticmethod
def _convert_temp(value, from_unit, to_unit):
if not isinstance(value, (int, float)):
raise ValueError("Temperature value must be a number.")
# Convert to Kelvin first
if from_unit == "K":
kelvin_val = value
elif from_unit == "C":
kelvin_val = value + 273.15
elif from_unit == "F":
celsius_val = (value - 32) * 5 / 9
kelvin_val = celsius_val + 273.15
else:
raise ValueError(f"Invalid temperature unit: {from_unit}. Use 'K', 'C', or 'F'.")
if kelvin_val < 0:
raise ValueError("Temperature cannot be below absolute zero (0 K).")
# Convert from Kelvin to target unit
if to_unit == "K":
return kelvin_val
elif to_unit == "C":
return kelvin_val - 273.15
elif to_unit == "F":
celsius_val = kelvin_val - 273.15
return celsius_val * 9 / 5 + 32
else:
raise ValueError(f"Invalid target temperature unit: {to_unit}. Use 'K', 'C', or 'F'.")
@staticmethod
def _convert_pressure(value, from_unit, to_unit):
if not isinstance(value, (int, float)):
raise ValueError("Pressure value must be a number.")
# Convert to Pascal first
if from_unit == "Pa":
pascal_val = value
elif from_unit == "kPa":
pascal_val = value * 1000
elif from_unit == "bar":
pascal_val = value * 100000
elif from_unit == "atm":
pascal_val = value * 101325
elif from_unit == "psi":
pascal_val = value * 6894.76
else:
raise ValueError(f"Invalid pressure unit: {from_unit}. Use 'Pa', 'kPa', 'bar', 'atm', or 'psi'.")
if pascal_val < 0:
raise ValueError("Pressure cannot be negative.")
# Convert from Pascal to target unit
if to_unit == "Pa":
return pascal_val
elif to_unit == "kPa":
return pascal_val / 1000
elif to_unit == "bar":
return pascal_val / 100000
elif to_unit == "atm":
return pascal_val / 101325
elif to_unit == "psi":
return pascal_val / 6894.76
else:
raise ValueError(f"Invalid target pressure unit: {to_unit}. Use 'Pa', 'kPa', 'bar', 'atm', or 'psi'.")
@staticmethod
def _convert_volume(value, from_unit, to_unit):
if not isinstance(value, (int, float)):
raise ValueError("Volume value must be a number.")
# Convert to cubic meters first
if from_unit == "m^3":
m3_val = value
elif from_unit == "L":
m3_val = value * 0.001
elif from_unit == "mL":
m3_val = value * 1e-6
else:
raise ValueError(f"Invalid volume unit: {from_unit}. Use 'm^3', 'L', or 'mL'.")
if m3_val < 0:
raise ValueError("Volume cannot be negative.")
# Convert from cubic meters to target unit
if to_unit == "m^3":
return m3_val
elif to_unit == "L":
return m3_val / 0.001
elif to_unit == "mL":
return m3_val / 1e-6
else:
raise ValueError(f"Invalid target volume unit: {to_unit}. Use 'm^3', 'L', or 'mL'.")
def _calculate_density(self):
"""Calculates and updates the density in kg/m^3."""
if self._moles is not None and self._molecular_weight is not None and self._volume is not None:
if self._moles > 0 and self._molecular_weight > 0 and self._volume > 0:
molecular_weight_kg_per_mol = self._molecular_weight / 1000 # g/mol to kg/mol
self._density = (self._moles * molecular_weight_kg_per_mol) / self._volume
return
self._density = None # Set density to None if any required component is missing or invalid
def _recalculate_state(self):
"""
Recalculates missing P, V, T, or n using the ideal gas law (PV = nRT)
if three of them are known. Then updates density.
"""
known_count = 0
if self._temp is not None and self._temp > 0: known_count += 1
if self._pressure is not None and self._pressure > 0: known_count += 1
if self._volume is not None and self._volume > 0: known_count += 1
if self._moles is not None and self._moles > 0: known_count += 1
# Attempt to calculate the missing variable if exactly three are known
try:
if known_count == 3:
if self._temp is None:
if self._pressure is not None and self._volume is not None and self._moles is not None:
self._temp = (self._pressure * self._volume) / (self._moles * self.R)
if self._temp <= 0: self._temp = None # ensure positive temp
elif self._pressure is None:
if self._temp is not None and self._volume is not None and self._moles is not None:
self._pressure = (self._moles * self.R * self._temp) / self._volume
if self._pressure <= 0: self._pressure = None # ensure positive pressure
elif self._volume is None:
if self._temp is not None and self._pressure is not None and self._moles is not None:
self._volume = (self._moles * self.R * self._temp) / self._pressure
if self._volume <= 0: self._volume = None # ensure positive volume
elif self._moles is None:
if self._temp is not None and self._pressure is not None and self._volume is not None:
self._moles = (self._pressure * self._volume) / (self.R * self._temp)
if self._moles <= 0: self._moles = None # ensure positive moles
except (TypeError, ZeroDivisionError):
# One of the known values was None or zero, which shouldn't happen if known_count == 3
# but good to catch if logic fails.
pass
self._calculate_density()
@property
def temperature(self):
"""Temperature in Kelvin."""
return self._temp
@temperature.setter
def temperature(self, value):
if not isinstance(value, (int, float)):
raise ValueError("Temperature must be a number.")
if value <= 0: # Kelvin must be positive
raise ValueError("Temperature in Kelvin must be positive.")
self._temp = value
self._recalculate_state()
@property
def pressure(self):
"""Pressure in Pascal."""
return self._pressure
@pressure.setter
def pressure(self, value):
if not isinstance(value, (int, float)):
raise ValueError("Pressure must be a number.")
if value <= 0:
raise ValueError("Pressure must be positive.")
self._pressure = value
self._recalculate_state()
@property
def volume(self):
"""Volume in cubic meters."""
return self._volume
@volume.setter
def volume(self, value):
if not isinstance(value, (int, float)):
raise ValueError("Volume must be a number.")
if value <= 0:
raise ValueError("Volume must be positive.")
self._volume = value
self._recalculate_state()
@property
def moles(self):
"""Moles."""
return self._moles
@moles.setter
def moles(self, value):
if not isinstance(value, (int, float)):
raise ValueError("Moles must be a number.")
if value <= 0:
raise ValueError("Moles must be positive.")
self._moles = value
self._recalculate_state()
@property
def molecular_weight(self):
"""Molecular weight in g/mol."""
return self._molecular_weight
@molecular_weight.setter
def molecular_weight(self, value):
if not isinstance(value, (int, float)):
raise ValueError("Molecular weight must be a number.")
if value <= 0:
raise ValueError("Molecular weight must be positive.")
self._molecular_weight = value
self._calculate_density() # Only density depends on molecular weight directly
def get_temperature(self, unit="K"):
"""Returns the temperature in the specified unit."""
if self._temp is None:
return None
return self._convert_temp(self._temp, "K", unit)
def get_pressure(self, unit="Pa"):
"""Returns the pressure in the specified unit."""
if self._pressure is None:
return None
return self._convert_pressure(self._pressure, "Pa", unit)
def get_volume(self, unit="m^3"):
"""Returns the volume in the specified unit."""
if self._volume is None:
return None
return self._convert_volume(self._volume, "m^3", unit)
def get_density(self, unit="kg/m^3"):
"""Returns the density in kg/m^3 (only one unit supported for density)."""
if unit != "kg/m^3":
raise ValueError("Density is only supported in kg/m^3.")
return self._density
def get_molecular_weight(self, unit="g/mol"):
"""Returns the molecular weight in g/mol (only one unit supported)."""
if unit != "g/mol":
raise ValueError("Molecular weight is only supported in g/mol.")
return self._molecular_weight
def get_moles(self):
"""Returns the number of moles."""
return self._moles
# Example Usage:
# Test Case 1: Initialize with T, P, V, n, M (all valid)
print("--- Test Case 1: Gas 1 (Nitrogen) ---")
gas1 = Gas(temp=25, temp_unit="C", pressure=1.0, pressure_unit="atm", volume=22.4, volume_unit="L", moles=1.0, molecular_weight=28.01)
print(f"Temperature: {gas1.get_temperature('C'):.2f} C")
print(f"Pressure: {gas1.get_pressure('atm'):.2f} atm")
print(f"Volume: {gas1.get_volume('L'):.2f} L")
print(f"Moles: {gas1.get_moles():.2f} mol")
print(f"Molecular Weight: {gas1.get_molecular_weight():.2f} g/mol")
print(f"Density: {gas1.get_density():.2f} kg/m^3")
print(f"Internal T: {gas1.temperature:.2f} K")
print(f"Internal P: {gas1.pressure:.2f} Pa")
print(f"Internal V: {gas1.volume:.2f} m^3")
print("-" * 30)
# Test Case 2: Recalculate Volume (missing V at init)
print("\n--- Test Case 2: Gas 2 (Recalculate Volume) ---")
gas2 = Gas(temp=300, pressure=101325, moles=1.0, molecular_weight=2.016) # Volume is missing, should be calculated
print(f"Initial Volume: {gas2.get_volume('L'):.2f} L")
gas2.pressure = gas2._convert_pressure(2.0, "atm", "Pa") # Double the pressure (setter expects Pa)
print(f"New Pressure: {gas2.get_pressure('atm'):.2f} atm")
print(f"Recalculated Volume: {gas2.get_volume('L'):.2f} L") # Volume should halve
print(f"Density: {gas2.get_density():.2f} kg/m^3")
print("-" * 30)
# Test Case 3: Recalculate Moles (missing n at init)
print("\n--- Test Case 3: Gas 3 (Recalculate Moles) ---")
gas3 = Gas(temp=273.15, pressure=101325, volume=0.0224, molecular_weight=32.0) # Moles missing
print(f"Initial Moles: {gas3.get_moles():.2f} mol") # Should be approx 1.0 mol
gas3.volume = gas3._convert_volume(44.8, "L", "m^3") # Double the volume (setter expects m^3)
print(f"New Volume: {gas3.get_volume('L'):.2f} L")
print(f"Recalculated Moles: {gas3.get_moles():.2f} mol") # Should be approx 2.0 mol
print(f"Density: {gas3.get_density():.2f} kg/m^3")
print("-" * 30)
# Test Case 4: Invalid Input
print("\n--- Test Case 4: Gas 4 (Invalid Input) ---")
try:
print("Attempting to create gas with negative Celsius temperature:")
Gas(temp=-300, temp_unit="C", pressure=1.0, pressure_unit="atm", volume=1.0, volume_unit="L", moles=1.0, molecular_weight=28.01)
except ValueError as e:
print(f"Error: {e}")
try:
print("\nAttempting to create gas with invalid pressure unit:")
Gas(temp=300, pressure=1.0, pressure_unit="invalid", volume=1.0, volume_unit="L", moles=1.0, molecular_weight=28.01)
except ValueError as e:
print(f"Error: {e}")
try:
print("\nAttempting to set molecular weight to non-positive:")
gas_test = Gas(temp=300, pressure=101325, volume=0.0224, moles=1.0, molecular_weight=32.0)
gas_test.molecular_weight = -10
except ValueError as e:
print(f"Error: {e}")
try:
print("\nAttempting to create gas with insufficient data to calculate P,V,T,n:")
gas_insufficient = Gas(temp=300, pressure=101325, molecular_weight=28.01) # only 2 out of 4 (T, P, V, n)
print(f"Moles: {gas_insufficient.get_moles()}") # Should be None
print(f"Volume: {gas_insufficient.get_volume('L')}") # Should be None
except Exception as e:
print(f"Unexpected error: {e}")
print("-" * 30)
# Test Case 5: Setting properties and observing density update
print("\n--- Test Case 5: Gas 5 (Setting properties) ---")
gas5 = Gas(temp=273.15, pressure=101325, volume=0.0224, moles=1.0, molecular_weight=28.01)
print(f"Initial Density: {gas5.get_density():.2f} kg/m^3")
# Change volume, density should change
gas5.volume = gas5._convert_volume(44.8, "L", "m^3")
print(f"Volume changed to {gas5.get_volume('L'):.2f} L. New Density: {gas5.get_density():.2f} kg/m^3")
# Change molecular weight, density should change
gas5.molecular_weight = 44.01 # CO2
print(f"MW changed to {gas5.get_molecular_weight():.2f} g/mol. New Density: {gas5.get_density():.2f} kg/m^3")
# Change temperature, volume should be recalculated, and density too
gas5.temperature = gas5._convert_temp(50, "C", "K")
print(f"Temp changed to {gas5.get_temperature('C'):.2f} C. Recalculated Volume: {gas5.get_volume('L'):.2f} L. New Density: {gas5.get_density():.2f} kg/m^3")
print("-" * 30)
# Test Case 6: Initialize with no molecular weight, then set it
print("\n--- Test Case 6: Gas 6 (No MW at init, then set) ---")
gas6 = Gas(temp=273.15, pressure=101325, volume=0.0224, moles=1.0)
print(f"Initial Density (MW missing): {gas6.get_density()}")
gas6.molecular_weight = 28.01
print(f"MW set to {gas6.get_molecular_weight():.2f} g/mol. New Density: {gas6.get_density():.2f} kg/m^3")
print("-" * 30)
Login to read full text