Electrolysis reactions in aqueous CuSO4 with Cu electrodes

Steps:

• At cathode (negative electrode): Cu²⁺ ions gain electrons to form Cu atoms, depositing reddish-brown copper solid (often described as pinkish in some contexts).
• At anode (positive electrode): Cu atoms from electrode lose electrons to form Cu²⁺ ions, dissolving into solution without gas evolution.
• Overall: Cu²⁺ concentration remains constant as anode dissolution replenishes ions lost at cathode.
• Solution stays blue; no color change or bubbles observed.

Why C is correct:

• Matches observations: copper deposit at cathode (1) and unchanged blue color (3), per electrode reactions maintaining ion balance.

Why the others are wrong:

• A includes 2 (bubbles), but anode dissolves without O₂ gas.
• B includes 2 (bubbles), incorrect as no gas forms.
• D excludes 1 (deposit), but Cu deposits at cathode.

Final answer: C