What is ΔH for the reaction represented by the equation 2Cu + S → Cu₂S if ΔH_f for Cu = 0, S = 0, and Cu₂S = -79.5 kJ/mol.

i'm assuming that the correct answer is indeed the first one/ "a"..

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.

it is b that is the answer.

im doing test rn im going with 2 but ill give answer if itss wrong,   : )