Question

When water is electrolysed, the gas collected at cathode is _________.

• A. sulphur
• B. oxygen
• C. hydrogen
• D. sulphur dioxide

Answer 1

The correct option is C hydrogen

During electrolysis, water decomposes to give hydrogen and oxygen gases due to passage of electric current. Electrolysis causes the water molecule to split, in which $H_3{O}^{+}$ hydronium ions move towards the cathode (negative electrode) and the $O{H}^{-}$ ions move towards the anode (positive electrode). The hydronium ions gain electrons liberating hydrogen at the cathode. The $O{H}^{-}$ ions releases electrons to form oxygen gas at anode.