(1) Q=qm=2.9×10 7J/kg×5×10 10kg=1.45×10 18J,
(2) V=
m
ρ =
1.2× 10 11 kg
1.98kg/ m 3 =6.06×10 10m 3
(3)已知 E=8.5×10 10kW?h=8.5×10 10×1000×3600J=3.06×10 17J,
Q=1.45×10 18J,η=
E
Q =
3.06 × 10 17 J
1.45× 10 18 J =21.1%;
答:(1)这些煤完全燃烧后,将放出为1.45×10 18J;
(2)这些二氧化碳气体在通常情况下的体积约为6.06×10 10m 3;
(3)火力发电站的效率为21.1%.