Liquid benzene (C₆H₆) burns in oxygen according to the equation 2C₆H₆(l) + 15O₂(g) → 12CO₂(g) + 6H₂O(g) How many litres of O₂ at STP are needed to complete the combustion of 39 g of liquid benzene? (Mol. wt. of O₂ = 32, C₆H₆ = 78)