According to the Arrhenius theory, an acid is a substance that

which produces hydrogen ion in water, called acid. A substance which produces hydroxide ion in water, called base. According to Bronsted-Lowry theory, an acid is proton donor and base is proton acceptor. Actually, Arrhenius theory is limited only to the aqueous solution.

Explanation:

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.