How many protons, neutrons, and electrons are in a neutral atom of Phosphorus, if its atomic number is 15 and its mass number is 30.97? 15 protons, 15 neutrons, 15 electrons
15 protons, 31 neutrons, 15 electrons
16 protons, 15 neutrons, 16 electron
15 protons, 16 neutrons, 15 electrons

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.

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

What is the mass of naoh that would have to be added to 500 ml of a solution of 0.20 m acetic acid in order to achieve a ph of 5.0?