The number of moles of copper electrolyzed =0.4g63.5g/mol=6.3×10−3mol
2 moles of electrons corresponds to 1 mole of copper.
Hence, 6.3×10−3mol moles of copper corresponds to 2×6.3×10−3mol=12.6×10−3mol of electrons.
The current at 1.2 amp is passed for additional 7 minutes.
Hence, the additional moles of electrons passed =1.2×7×6096500=5.22×10−3.
Hence, total number of moles of electrons passed 12.6×10−3mol+5.22×10−3mol=17.82×10−3mol .
The volume of oxygen liberated at NTP 17.82×10−3mol4×22400=99.68ml