Why is it difficult to determine whether lipase is active in tube 5 [the one where you added vegetable oil, bile slats, lipase and a buffer with a pH of 2.0]

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).

they are all solids.