Từ các dữ kiện sau: C (than chì) + O2(k) → CO2(k) H1 = -393,5kJ
H2(k) + 1/2O2(k) → H2O (l) H2 = -285,8kJ
2C2H6(k) + 7O2(k) → 4CO2(k) + 6H2O(l) H3 = -3119,6kJ
Tính biến thiên entanpi chuẩn của phản ứng ở cùng điều kiện:
2C(than chì) + 3H2(k) → C2H6(k) H4 = ?

Skills of homo sapiens were found an excavation. the skulls were preserved because the bodies were frozen. so, these fossils are (blank) fossils.the image shows the evolution of skulls beginning 2 to 3 million years ago. based on the image, modern human skulls(blank) ape skulls.