def calc_activity(X, gamma):
	"""
	Returns the value of the activity of any species given the concentration of that species in
	mol fraction, X, and the activity coefficient gamma.

	Parameters
	----------
	X: float
		Concentration of the given species in mol fraction

	gamma: float
		Activity coefficient of the given species

	Returns
	-------
	float
		Activity of the given species
	"""

	return X * gamma