How many moles of water vapour are formed when 10 litres of butane gas c4h10 is burned in oxygen at stp?

2C4H10 + 13O2 ==> 8CO2 + 10H2O

moles C4H10 in 10 L = 10/22.4 = 0.446
0.446 moles C4H10 x (10 mols H2O/2 mols C4H10) = 0.446 x 5 = ?