The frequency of collisions between the N₂ and H₂ molecules will decrease and the rate of reaction will also decrease.
Since the water is cooler than the gas mixture, heat will flow from the gas to the water.
The gas will cool down, so the average kinetic energy of the gas molecules will decrease.
The molecules will be moving more slowly, so there will be <em>fewer collisions</em> and <em>fewer of these collisions will have enough energy to react</em>.
The rate of reaction between H₂ and N₂ molecules at room temperature is exceedingly slow, <em>but cooling the gas mixture will make the reaction even slower</em>.
If you follow the octet rule, you know that an element must have 8 outside (or valence) electrons to be energetically favorable.
In CCl4, the carbon molecule forms four bonds; one for each chlorine atom. Each bond contains 2 electrons, so it is satisfied.
In PCl3, Phosphorous forms only 3 bonds with chlorine, which means in order to have 8 valence electrons, it also has a lone pair of electrons, not bonded with chlorine.
Now, in CCl4, picture the shape of the molecule like a plus sign, with the carbon in the middle and the chlorine at the four ends. It is symmetrical, and therefore is nonpolar.
In PCl3, the lone pair electrons <em>push</em>, so to speak, the 3 chlorine atoms away, making a T-shaped molecule. Since the chlorine is more electronegative than carbon, the molecule is unbalenced, making it polar.
