If 5.100 g of c6h6 is burned and the heat produced from the burning is added to 5691 g of water at 21 °c, what is the final temperature of the water?

  C6H12 = 6x12 + 6x1 = 78. 
The equation indicates that 2x78 = 156g benzene will produce 6542kJ. 
Using proportions you can then calculate that 
x/6542kJ = 7.9g / 156g 
x = 331.3kJ = 331300J. 

heat = mass x ΔT x 4.18J/g° 
ΔT = 331300J / (5691g x 4.18J/g°) = 13.9° 

final temp = 21 + 14° = 35°C