def set_species_mol_fractions(mol_fractions, user_species_dictionary):
    """
        Creates a mol_fraction dictionary for cantera simulation

        =========================== =======================================================================
        Input                       Description
        =========================== =======================================================================
        mol_fractions               A dictionary with user names as keys and mol fractions as values
        user_species_dictionary     A dictionary with user names as keys and species objects as values
        ===================================================================================================

        =========================== =======================================================================
        Output                      Description
        =========================== =======================================================================
        cantera_mol_fractions       A dictionary with species objects as keys and mol fractions as values
        ===================================================================================================
    """

    cantera_mol_fractions = {}
    for (user_name, mol_frac) in mol_fractions.iteritems():
        cantera_mol_fractions[user_species_dictionary[user_name]] = mol_frac

    return cantera_mol_fractions