Answer is: 7. Lewis base. Nitrogen trifluoride (NF₃) a Lewis base, because it can donate its lone pair of electrons (lone pair of electrons are in nitrogen atom). Lewis base is any species that has a filled orbital containing an electron pair which is not involved in bonding but may form a dative bond with a Lewis acid. Nitrogen-fluorine compound is a colorless, odorless and nonflammable gas.
Haber's process is used for the industrial production of ammonia. The process conditions at which maximum yield can be obtained, include 15-20mPa pressure, 400-500 degrees Celsius of the temperature, use of methane as a source of hydrogen, use of iron-based catalysts and combined with K2O, CaO, SiO2, and Al2O3. Reuse of unreacted gases can lead to the achievement of 97% yield.