For how long must a current of 2 amplitude be pass fair aqeous solution of a copper salt during electrolysis in order to deposit 2.50 gram of copper (cu=63.5)
96,485 coulombs will deposit 63.5/2 or 31.75 g Cu. You want to deposit 2.5 g Cu so you want 96,485 coulombs x (2.50/31.75) = ? coulombs.
Coulombs = amperes x seconds
You know coulombs and amperes, solve for seconds.
Post your work if you get stuck.