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 = ?

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

a pan containing water is placed in a positio n where it is exposed to a 10 mile per hour wind. the pan contains a uniform depth of 1.27 cm of water, is quite wide, and has a length of 2.44 m in the wind direction. the water in the pan is at a constant temperature of 15.5 °c.