Add molecular_chemistry.py (#2944)

* Create molecular_chemistry.py

* round up outputs

* Remove floating point

* Add Wikipedia references

* fixup! Format Python code with psf/black push

* Add Conversions/Molecular Chemistry

* updating DIRECTORY.md

* Update molecular_chemistry.py

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>

DIRECTORY.md

@@ -100,6 +100,7 @@
   * [Decimal To Hexadecimal](https://github.com/TheAlgorithms/Python/blob/master/conversions/decimal_to_hexadecimal.py)
   * [Decimal To Octal](https://github.com/TheAlgorithms/Python/blob/master/conversions/decimal_to_octal.py)
   * [Hexadecimal To Decimal](https://github.com/TheAlgorithms/Python/blob/master/conversions/hexadecimal_to_decimal.py)
+  * [Molecular Chemistry](https://github.com/TheAlgorithms/Python/blob/master/conversions/molecular_chemistry.py)
   * [Prefix Conversions](https://github.com/TheAlgorithms/Python/blob/master/conversions/prefix_conversions.py)
   * [Roman To Integer](https://github.com/TheAlgorithms/Python/blob/master/conversions/roman_to_integer.py)
   * [Temperature Conversions](https://github.com/TheAlgorithms/Python/blob/master/conversions/temperature_conversions.py)

conversions/molecular_chemistry.py

@@ -0,0 +1,92 @@
+"""
+Functions useful for doing molecular chemistry:
+* molarity_to_normality
+* moles_to_pressure
+* moles_to_volume
+* pressure_and_volume_to_temperature
+"""
+
+
+def molarity_to_normality(nfactor: int, moles: float, volume: float) -> float:
+    """
+    Convert molarity to normality.
+      Volume is taken in litres.
+
+      Wikipedia reference: https://en.wikipedia.org/wiki/Equivalent_concentration
+      Wikipedia reference: https://en.wikipedia.org/wiki/Molar_concentration
+
+      >>> molarity_to_normality(2, 3.1, 0.31)
+      20
+      >>> molarity_to_normality(4, 11.4, 5.7)
+      8
+    """
+    return round((float(moles / volume) * nfactor))
+
+
+def moles_to_pressure(volume: float, moles: float, temperature: float) -> float:
+    """
+    Convert moles to pressure.
+      Ideal gas laws are used.
+      Temperature is taken in kelvin.
+      Volume is taken in litres.
+      Pressure has atm as SI unit.
+
+      Wikipedia reference: https://en.wikipedia.org/wiki/Gas_laws
+      Wikipedia reference: https://en.wikipedia.org/wiki/Pressure
+      Wikipedia reference: https://en.wikipedia.org/wiki/Temperature
+
+      >>> moles_to_pressure(0.82, 3, 300)
+      90
+      >>> moles_to_pressure(8.2, 5, 200)
+      10
+    """
+    return round(float((moles * 0.0821 * temperature) / (volume)))
+
+
+def moles_to_volume(pressure: float, moles: float, temperature: float) -> float:
+    """
+    Convert moles to volume.
+      Ideal gas laws are used.
+      Temperature is taken in kelvin.
+      Volume is taken in litres.
+      Pressure has atm as SI unit.
+
+      Wikipedia reference: https://en.wikipedia.org/wiki/Gas_laws
+      Wikipedia reference: https://en.wikipedia.org/wiki/Pressure
+      Wikipedia reference: https://en.wikipedia.org/wiki/Temperature
+
+      >>> moles_to_volume(0.82, 3, 300)
+      90
+      >>> moles_to_volume(8.2, 5, 200)
+      10
+    """
+    return round(float((moles * 0.0821 * temperature) / (pressure)))
+
+
+def pressure_and_volume_to_temperature(
+    pressure: float, moles: float, volume: float
+) -> float:
+    """
+    Convert pressure and volume to temperature.
+      Ideal gas laws are used.
+      Temperature is taken in kelvin.
+      Volume is taken in litres.
+      Pressure has atm as SI unit.
+
+      Wikipedia reference: https://en.wikipedia.org/wiki/Gas_laws
+      Wikipedia reference: https://en.wikipedia.org/wiki/Pressure
+      Wikipedia reference: https://en.wikipedia.org/wiki/Temperature
+
+      >>> pressure_and_volume_to_temperature(0.82, 1, 2)
+      20
+      >>> pressure_and_volume_to_temperature(8.2, 5, 3)
+      60
+    """
+    return round(float((pressure * volume) / (0.0821 * moles)))
+
+
+if __name__ == "__main__":
+
+    import doctest
+
+    doctest.testmod()