Read the given chemical reaction.

c2h6 + o2 → co2 + h2o

how many moles of h2o are produced during the complete combustion of 1.4 moles of c2h6?

2.8 moles
4.2 moles
5.6 moles
7.0 moles

the balanced equation for the combustion of ethane is as follows

2C₂H₆ + 7O₂ --> 4CO₂  + 6H₂O

molar ratio of C₂H₆ to H₂O is 2:6

this means that when 2 mol of C₂H₆ react 6 mol of H₂O are produced

for every 1 mol of C₂H₆ that reacts  thrice the number of  moles of H₂O are produced

therefore when 1.4 mol of C₂H₆ reacts - 3 x 1.4  = 4.2 mol of H₂O are produced

the answer is 4.2 mol

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)