2Нг + Oj —» 2НгО. A mixture o f hydrogen and oxygen can be kept for years but we can
observe no appreciable reaction taking place.
That is why it is not unusual to hear chcmists speaking about the factors
that determine the rate of a reaction. These are manifold. The rate depends
not only upon the composition of the reacting substances, but also upon
their physical form, the intimacy o f their mixture, the temperature and
pressure, the concentrations o f the reactants, spccial physical circumstances
such as irradiation with visible light, ultraviolet light, X-rays, neutrons, or
other waves or particles, and the presence of other substances that affect
the reaction but arc not changed by it.
W ords a n d W o rd -C o m b in atio n s to Be M em orized
