Answer is 16
carbon valence = 4
oxygen valence = 6 but carbon dioxide have 2 oxygen so = 12
12 + 4 = 16
so carbon dioxide have 16 electron
C4h10+6.5o2=4co2+5h2o
moles of butane=1.92/58=0.0331 moles
moles of water=0.1655 moles\
as the butane and water has 1 is to 5 molar ratio
0.1655=mass/18
mass=2.98 g
mass of water produced = 2.98 g
