Given the following heats of formation. Calculate the heat of combustion of each compound in kJ mole -1 . The product in each case
will be CO 2(g) and H 2 O (l) .
(a) ethane, C 2 H 6(g) , -107 kJ mole -1
(b) acetylene, C 2 H 2(g) , +227 kJ mole -1
(c) benzoic acid, C 7 H 6 O 2(s) , -390 kJ mole -1

Two nitro no2 groups are chemically bonded to a patch of surface. they can't move to another location on the surface, but they can rotate (see sketch at right). it turns out that the amount of rotational kinetic energy each no2 group can have is required to be a multiple of ε, where =ε×1.010−24 j. in other words, each no2 group could have ε of rotational kinetic energy, or 2ε, or 3ε, and so forth — but it cannot have just any old amount of rotational kinetic energy. suppose the total rotational kinetic energy in this system is initially known to be 32ε. then, some heat is removed from the system, and the total rotational kinetic energy falls to 18ε. calculate the change in entropy. round your answer to 3 significant digits, and be sure it has the correct unit symbol.

The chemical bond connecting one nucleotide with the next one along the nucleic acid chain is called a

Ants live on acacia trees in south america. the ants feed on sugars secreted by the trees. the trees provide room for the ants to live. the ants sting any other insect or animal that comes to eat the trees. what type of relationship is this?